Physics Letters B 796 (2019) 230–252 Contents lists available at ScienceDirect Physics Letters B www.elsevier.com/locate/physletb √ Measurement of prompt photon production in sNN = 8.16 TeV p + Pb collisions with ATLAS .The ATLAS Collaboration  a r t i c l e i n f o a b s t r a c t √ Article history: The inclusive production rates of isolated, prompt photons in p + Pb collisions at sNN = 8.16 TeV Received 7 March 2019 are studied with the ATLAS detector at the Large Hadron Collider using a dataset with an integrated Received in revised form 19 June 2019 luminosity of 165 nb−1 recorded in 2016. The cross-section and nuclear modification factor R pPb are Accepted 15 July 2019 measured as a function of photon transverse energy from 20 GeV to 550 GeV and in three nucleon– Available online 17 July 2019 nucleon centre-of-mass pseudorapidity regions, (−2.83, −2.02), (−1.84, 0.91), and (1.09, 1.90). The Editor: M. Doser cross-section and R pPb values are compared with the results of a next-to-leading-order perturbative QCD calculation, with and without nuclear parton distribution function modifications, and with expectations based on a model of the energy loss of partons prior to the hard scattering. The data disfavour a large amount of energy loss and provide new constraints on the parton densities in nuclei. © 2019 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3 . 1. Introduction from both initial- and final-state. Due to the significantly simpler underlying-event conditions in proton–nucleus collisions, measure- Measurements of particle and jet production rates at large ments of photon rates can be performed with better control over transverse energy are a fundamental method of characterising systematic uncertainties than in nucleus–nucleus collisions, allow- hard-scattering processes in all collision systems. In collisions in- ing a more precise constraint on these initial-state effects. volving large nuclei, production rates are modified from those Prompt photon production has been extensively measured in measured in proton + proton (pp) collisions due to a combina- pp collisions at a variety of collision energies [8–12] at the Large tion of initial- and final-state effects. The former arise from the Hadron Collider (LHC). It was also measured in lead–lead (Pb+Pb) √ dynamics of partons in the nuclei prior to the hard-scattering pro- collisions at a nucleon–nucleon centre-of-mass energy s = √ NN cess, while the latter are attributed to the strong interaction of 2.76 TeV [13,14] at the LHC, and in gold–gold collisions at sNN = the emerging partons with the hot nuclear medium formed in 200 GeV at the Relativistic Heavy Ion Collider (RHIC) [15], where nucleus–nucleus collisions. Modification due to the nuclear en- the data from both colliders indicate that photon production rates vironment is quantified by the nuclear modification factor, R AA , are unaffected by the passage of the photons through the hot nu- defined as the ratio of the cross-section measured in A + A to clear medium. At RHIC, photon production rates were measured √ that in pp collisions, scaled by the expected geometric difference in deuteron–gold collisions at sNN = 200 GeV [16,17] and were between the systems. found to be in good agreement with perturbative QCD (pQCD) Measurements of prompt photon production rates offer a way calculations. Additionally, jet production [18,19] and electroweak to isolate the initial-state effects because the final-state photons boson production [20–22] were measured in 28 nb−1 of proton– √ do not interact strongly. These initial-state effects include the de- lead (p + Pb) collision data at sNN = 5.02 TeV recorded at the gree to which parton densities are modified in a nuclear envi- LHC; the former is a strongly interacting final state, while the latter ronment [1–3], as well as potential modification due to an en- is not. All measurements provided some constraints on initial-state ergy loss arising through interactions of the partons traversing effects. the nucleus prior to the hard scattering [4,5]. Constraints on such The data used in this measurement were collected with the AT- initial-state effects are particularly important for characterising the LAS detector during the p + Pb collision running period in 2016, observed modifications of strongly interacting final states, such as and correspond to an integrated luminosity of 165 nb−1 , approx- jet and hadron production [6,7], since they are sensitive to effects imately six times larger than the measurements made in the pre- vious 5.02 TeV data. The proton and lead beams had an energy of 6.5 TeV and 2.51 TeV per nucleon respectively, resulting in a  E-mail address: atlas.publications@cern.ch. nucleon–nucleon centre-of-mass collision energy of 8.16 TeV and https://doi.org/10.1016/j.physletb.2019.07.031 0370-2693/© 2019 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3 . The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 231 a rapidity boost of this frame by ±0.465 units relative to the AT- is immersed in a 2 T axial magnetic field and provides  charged- LAS laboratory frame, depending on the direction of the Pb beam.1 particle tracking in the pseudorapidity range ηlab  < 2.5 in the By convention, the results are reported as a function of photon laboratory frame. In order of closest to furthest from the beam pseudorapidity in the nucleon–nucleon collision frame, η∗ , with pipe, it consists of a high-granularity silicon pixel detector, a sil- positive η∗ corresponding to the proton beam direction, and nega- icon microstrip tracker, and a transition radiation tracker. Addi- tive η∗ corresponding to the Pb beam direction. tionally, the new insertable B-layer [28] has been operating as the At leading order, the process p + Pb → γ + X has contributions innermost layer of the tracking  system  since 2015. The calorime-   from direct processes, in which the photon is produced in the hard ter system covers the range ηlab  < 4.9. In the region ηlab  < interaction, and from fragmentation processes, in which it is pro- 3.2, electromagnetic calorimetry is provided by barrel and end- duced in the parton shower. Beyond leading order the direct and cap high-granularity lead/liquid-argon (LAr) sampling   calorimeters. fragmentation components are not separable and only their sum is An additional thin LAr presampler covers ηlab  < 1.8 to cor- a physical observable. rect for energy loss in material before the calorimeters. The LAr To reduce contamination from the dominant background of calorimeters are divided into three layers in radial depth. Hadronic photons mainly from light-meson decays in jets, the measurements calorimetry is provided by a steel/scintillator-tile  calorimeter, seg- presented here require the photons to be isolated from nearby mented into three barrel structures within ηlab  < 1.7, and two particles. This requirement also acts to reduce the relative contri- copper/LAr   hadronic endcap calorimeters, which cover the region bution of fragmentation photons in the measurement, and thus, 1.5 < ηlab  < 3.2. Finally, the forward calorimeter covers 3.2 <  lab  the same fiducial requirement must be imposed on theoretical η  < 4.9 and is divided into three compartments. The first com- models when comparing with the data. Specifically, as in pre- partment is a copper/LAr electromagnetic calorimeter, while the vious ATLAS measurements [9,10], the sum  of energy transverse remaining two tungsten/LAr calorimeter compartments collect the to the beam axis within a cone of  R ≡ (η)2 + (φ)2 = 0.4 hadronic energy. around the photon, E Tiso , is required to be smaller than 4.8 + 4.2 × During data-taking, events were initially selected using a level-1 γ γ 10−3 E T [GeV], where E T is the transverse energy of the photon. trigger, implemented in custom electronics, based on energy de- iso At particle level, E T is calculated as the sum of transverse energy position in the electromagnetic calorimeter. The high-level trigger γ of all particles with a decay length above 10 mm, excluding muons [29] was then used to select events consistent with a high-E T and neutrinos. This sum is corrected for the ambient contribution photon candidate. The high level trigger was configured with five γ from underlying-event particles, consistent with the previous mea- online E T thresholds from 15 GeV to 35 GeV. Each trigger is γ surements [9,10]. used for an exclusive region of the E T spectrum, starting 5 GeV This letter reports a measurement of the cross-section for above the trigger threshold because there the trigger is fully ef- √ prompt, isolated photons in p + Pb collisions at sNN = 8.16 TeV. ficient. The highest-threshold trigger is used in the measurement γ γ over the whole E T range above 40 GeV and is unprescaled. The Photons are measured with E T > 20 GeV, the isolation require- ment detailed above, and in three nucleon–nucleon centre-of-mass lower-threshold, prescaled, triggers are used to perform the mea- γ pseudorapidity (η∗ ) regions, −2.83 < η∗ < −2.02, −1.84 < η∗ < surement for E T in the range of 20–40 GeV. 0.91, and 1.09 < η∗ < 1.90. In addition to the cross-section, the Data-taking was divided into two periods with different con- data are compared to a pp reference cross-section derived from a figurations of the LHC beams. In the first period, the lead ions previous √ measurement of prompt photon production in pp colli- circulated in beam 1 (clockwise) and protons circulated in beam 2, sions at s = 8 TeV that used the identical isolation condition [9]. while in the second period the beams were reversed. These periods The nuclear modification factor R pPb is derived in each pseudo- corresponded to integrated luminosities of 57 nb−1 and 108 nb−1 rapidity region, using an extrapolation for the different collision respectively. energy and centre-of-mass pseudorapidity selection, and is re- γ 3. Photon reconstruction and identification ported in the region E T > 25 GeV where reference data is avail- able. Furthermore, the ratio of R pPb in the forward region to that in the backward region is presented. The measurements are com- Photons are reconstructed following a procedure used exten- sively in previous ATLAS measurements [10], of which only the pared with next-to-leading-order (NLO) pQCD predictions from main features are summarised here. Jetphox [23] using parton distribution functions (PDF) extracted Photon candidates are reconstructed from clusters of energy de- from global analyses that include nuclear modification effects anal- posited in the electromagnetic calorimeter in three regions corre- yses [24,25]. Additionally, the data are compared with predictions lab from a model including initial-state energy loss [4,5,26].  (η  ) positions of the barrel and sponding to the laboratory-frame forward and backward endcaps ηlab  < 2.37. The transition region   2. Experimental set-up between the barrel and endcap calorimeters, 1.37 < ηlab  < 1.56, is excluded due to its higher level of inactive material. The mea- The ATLAS detector [27] is a multipurpose detector with a surement of the photon energy is based on the energy collected forward–backward symmetric cylindrical geometry. For this mea- in calorimeter cells in an area of size η × φ = 0.075 × 0.175 in surement, its relevant components include an inner tracking de- the barrel and η × φ = 0.125 × 0.125 in the endcaps. It is cor- tector surrounded by a thin superconducting solenoid, and elec- rected via a dedicated energy calibration [30] which accounts for losses in the material before the calorimeter, both lateral and lon- tromagnetic and hadronic calorimeters. The inner-detector system gitudinal leakage, and for variation of the sampling-fraction with energy and shower depth. 1 ATLAS uses a right-handed coordinate system with its origin at the nominal The photons are identified using the tight calorimeter shower interaction point (IP) in the centre of the detector and the z-axis along the beam shape requirements described in Ref. [31]. The tight requirements pipe. The x-axis points from the IP to the centre of the LHC ring, and the y-axis select clusters which are compatible with originating from a single points upward. Cylindrical coordinates (r , φ) are used in the transverse plane, φ photon impacting the calorimeter. The information used includes being the azimuthal angle around the z-axis. The pseudorapidity is defined in terms of the polar angle θ as η = − ln tan(θ/2) and the rapidity of the components of the that from the hadronic calorimeter, the lateral shower shape in the beam, y, are defined in terms of their energy, E, and longitudinal momentum, p z , second layer of the electromagnetic calorimeter, and the detailed E+p as y = 0.5 ln E − p z . shower shape in the finely segmented first layer. z 232 The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 The isolation transverse energy, E Tiso , is computed from the sum dσ 1 1 N sig P sig γ = C MC , of E T values in topological clusters of calorimeter cells [32] inside dE T L int  E Tγ sel trig a cone of size  R = 0.4 centred on the photon. This cone size is γ chosen to be compatible with a√previous measurement of photon where L int is the integrated luminosity,  E T is the width of the γ production in pp collisions at s = 8 TeV [9], which is used to E T bin, N sig is the yield of photon candidates passing identifica- construct the reference spectrum for the R pPb measurement. This tion and isolation requirements, P sig is the purity of the signal estimate excludes an area of η × φ = 0.125 × 0.175 centred on selection, sel is the combined reconstruction, identification and the photon, and is corrected for the expected leakage of the photon isolation efficiency for signal photons, trig is the trigger efficiency, energy from this region into the isolation cone. and C MC is a MC derived bin-by-bin correction for the change γ in the E T spectrum from photons migrating between bins in the 4. Simulated event samples spectrum due to the width in the energy response. C MC is deter- mined after all selection criteria at both reconstruction and particle Samples of Monte Carlo (MC) simulated events were gener- levels are imposed. ated to study the detector performance for signal photons. Proton– Trigger efficiencies trig are studied using events selected with proton generators were used as the source of events containing minimum-bias triggers, level-1 triggers without additional require- photons. To include the effects of the p + Pb underlying-event en- ments, and photon high-level triggers without identification re- vironment, these simulated pp events were combined with p + Pb quirements. They are greater than 99.5% for all triggers [29]. In events from data before reconstruction. In this way, the simulated this analysis they are taken as trig = 1, and any uncertainty is ne- events contain the effects of the p + Pb underlying-event identical glected as being sub-dominant to other uncertainties. to those observed in data. The purity P sig is determined via a double-sideband procedure The Pythia 8.186 [33] generator was used to generate the nom- used extensively in previous measurements of cross-sections for inal set of MC events, with the NNPDF23LO parton distribution processes with a photon in the final state [9,10,40,41] and sum- function (PDF) set [34] and a set of generator parameters tuned marised here. In the procedure, four regions are defined which to reproduce minimum-bias pp events with the same collision en- categorise photon candidates along two axes: (1) isolation, corre- ergy as that in the p + Pb data (“A14” tune) [35]. A centre-of-mass sponding to an isolated and an inverted “non-isolated” selection; boost was applied to the generated events to bring them into the (2) identification, corresponding to photons that pass the tight same laboratory frame as the data. The generator simulates the identification requirements described in Ref. [31], and those that direct photon contribution and, through final-state QED radiation pass the loose requirements of Ref. [31] but fail certain components in 2 → 2 QCD processes, also includes the fragmentation photon of the tight requirements, designed to mostly select background. contributions; these components are defined to be signal photons. The majority of signal photons are in the tight, isolated region, de- γ fined to be the signal region, while the other three regions are Events were generated in six exclusive E T ranges from 17 GeV to 500 GeV. dominated by the background. Photon candidates that comprise An additional MC sample was used to assess the sensitiv- the background are assumed to be distributed in a way that is un- ity of the measurement to this choice of generator. The Sherpa correlated along the two axes. The yields in the three non-signal 2.2.4 [36] event generator produces fragmentation photons in a dif- sidebands are used to estimate the yield of background in the sig- ferent way from Pythia and was thus chosen for the comparison. nal region and is combined with the yield in the signal region to The NNPDF3.0NNLO PDF set [37] was used, and the events were extract the purity. The procedure also accounts for the small frac- generated in the same kinematic regions as the Pythia events. tion of signal photons which are reconstructed in the non-signal These events were generated with leading-order matrix elements sidebands; these quantities, known as leakage fractions, are deter- for photon-plus-jet final states with up to three additional partons, mined from the simulation samples described in Section 4. The pu- γ γ which were merged with the Sherpa parton shower. The Sherpa rity is typically 45% at E T = 20 GeV, rises to 80% at E T = 100 GeV γ sample produced results consistent with Pythia, and, thus, no cor- and reaches 99% at E T = 300 GeV. rection or uncertainty is applied. Fig. 1 shows example E Tiso distributions for identified and iso- The Pythia and Sherpa pp events were passed through a full lated photons, the corresponding distributions for background pho- Geant4 simulation of the ATLAS detector [38,39]. To model the un- tons with the normalisation determined by the double-sideband derlying event effects, each simulated event was combined with a method, and the resulting signal-photon distributions after back- minimum-bias p + Pb data event and the two were reconstructed ground subtraction, compared with those for generator-level pho- together as a single event, using the same algorithms as used for tons in MC simulation. The figure shows the shape of the back- the data. These events were split between the two beam con- ground distribution within the signal region, and the correspon- figurations in a proportion matched to that in data-taking. The dence between the background-subtracted data and the signal-only underlying event activity levels, as characterized by the sum of Pythia 8 distributions gives confidence that the simulations accu- the transverse energy in the outgoing-Pb-beam side of the for- rately represent the data. ward calorimeter (3.1 < |ηlab | < 4.9), are different in the photon- The photon selection efficiency is determined from MC sim- containing data events from the minimum-bias data events used ulations. Generated prompt photons are required to be isolated in the simulation. Thus, the simulated events were weighted on a at the generator level, after an estimate of the underlying event per-event basis to match the underlying event activity distribution has been subtracted from the isolation energy, as described above. in data. Furthermore, the photon shower shapes and identification Reconstruction efficiency is determined by requiring a photon to efficiency in simulation were adjusted for small differences pre- have been reconstructed within  R = 0.2 of the generated pho- viously observed between these quantities in data and in Geant4 ton. Reconstructed photons matching to a generated photon are simulation [31]. further required to satisfy tight identification and isolation crite- ria defined in Section 1. The combined efficiency of signal photons 5. Data analysis to pass all reconstruction level selections, sel , is typically 90% at γ γ all E T and η∗ , except at E T ≈ 20 GeV where it decreases to about γ The differential cross-section is calculated for each E T and η∗ 80%. Fig. 2 summarises the different components of the total selec- bin as tion efficiency. The reconstruction efficiency is 96–99% everywhere, The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 233 Fig. 1. Distributions of detector-level photon isolation transverse energy E Tiso for identified photons in data (black points), background photons scaled to match the data at large E Tiso (blue solid line), the resulting distribution for signal photons scaled so that the maximum value is the same as that for identified photons (green dot-dashed line), and that for photons in simulation which are isolated at the generator level normalised to have the same integral as the signal photon distribution (red dashed line). Each γ γ panel shows a different pseudorapidity region, while the top and bottom panels show the low-E T and high-E T range respectively. The vertical error bars represent statistical uncertainties only. γ Fig. 2. Efficiency for simulated photons passing the generator-level isolation requirement, shown as a function of photon transverse energy E T with a different pseudorapidity region in each panel. The reconstruction (red circles), reconstruction plus identification (blue squares) and total selection (green triangles) efficiencies are shown separately. γ γ with the lowest values at the lowest E T . The isolation efficiency increasing E T due to the difficulty of separating conversion elec- γ is lowest at high E T , most likely because the associated prod- trons at high energy. ucts of fragmentation photons are, on average, more energetic and In MC events, the E T response for prompt, isolated photons, de- collimated when the energy of the photon is higher. The largest fined as the ratio of the reconstructed to generator E T , is found to inefficiency is due to the identification requirements. This identi- be within 1% of unity, with a resolution that decreases from 3% γ γ fication efficiency is lowest at 20 GeV and increases with E T as to 2% over the E T range of the measurement. The bin migration higher-energy photons create larger and more identifiable showers correction factors C MC are determined using the event simula- in the calorimeter. It peaks around 100 GeV, and decreases with tions described in Section 4. They are defined as the bin-by-bin 234 The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 √ ergy s = 8 TeV with its rest frame corresponding with that of the laboratory reference frame. That is, the cross-sections in the numerator and denominator use the same ηlab regions, although in the former case this corresponds to a different centre-of-mass pseudorapidity. These factors are shown in Fig. 3 and are applied as multiplicative factors to the measured 8 TeV data. They are dominated by the effect from the boost of the p + Pb system, as the effect due to the difference in collision energy alone is less γ γ than 1% for all E T . For −1.84 < η∗ < 0.91, or E T < 100 GeV at large rapidities, the factors are typically within a few percent of γ unity. However, at large E T , where the rapidity distribution be- comes steeper, the extrapolation factors become more sensitive to the rapidity shift from the centre-of-mass boost between the frames, and at large pseudorapidity they reach a factor of 2–3. An alternative set of factors, derived from the generator-level predic- tions of Pythia 8, are also shown in Fig. 3; these are used to assess γ the sensitivity of the extrapolation factors to the rapidity and E T √ dependence of the model cross sections. Fig. 3. Summary of extrapolation factors applied to the measured pp s = 8 TeV √ data to construct an approximate s = 8.16 TeV spectrum matching the shift of the centre-of-mass in p + Pb data plotted as a function of generator-level photon trans- 6. Systematic uncertainties verse energy. Here η represents the boost of the centre-of-mass frame of 0.465. The factors determined using Jetphox (dashed lines) and Pythia 8 (solid lines) are shown for the three ηlab ranges used in the measurement (different colours). The The sources of systematic uncertainties affecting the measure- relative difference between these two extrapolation methods is taken as a system- ment are described in this section, which is broken into two parts atic uncertainty. discussing the uncertainty in 1) the cross-section and 2) the nu- part clear modification factor R pPb , including its ratio between forward ratio C MC = N MC / N MC reco of the reconstructed, identified, and iso- and backward pseudorapidity regions. γ part lated photon E T spectrum, where N MC is the number in a given γ reco E T bin at the particle level and N MC is the number in the corre- 6.1. Cross-section uncertainty sponding bin at the reconstruction level. The nuclear modification factor R pPb can be expressed as a ratio The major uncertainties in the cross-section can be divided of cross-sections in the following way: into two main categories: those affecting the purity determination, γ which are dominant at low E T where the sample purity is low, R pPb = (dσ p +Pb→γ + X /dE T )/( A · dσ pp →γ + X /dE T ) , γ γ (1) and those affecting the detector performance corrections, which γ where the geometric factor A is simply the number of nucleons in are dominant at high E T . All other sources tend to be weakly γ the Pb nucleus, 208. The dependent on E T . A summary is shown in Fig. 4. In each cate- √ reference pp spectrum is constructed us- ing measurements of s = 8 TeV pp data by ATLAS [9] that use the gory, the uncertainty is the sum in quadrature of the individual same particle-level isolation requirement. The 8 TeV measurements components; the combined uncertainty is the sum in quadrature in the regions |ηlab | < 1.37 and 1.56 < |ηlab | < 2.37 are used as the of all contributions, excluding those associated with the luminos- γ reference spectra for the central and the forward and backward ra- ity. The total uncertainties range from 15% at low and high E T , pidity data, after applying a multiplicative correction for the effects where they are dominated by the purity and detector performance of the boost in the 8.16 TeV p + Pb system. For each kinematic uncertainties respectively, to a minimum of approximately 6% at γ region, extrapolation factors are determined as the ratio of pho- E T ≈ 100 GeV, where both of these uncertainties are modest. ton cross sections To assess the uncertainty in the purity determination, each √ from Jetphox calculations for pp collisions. The numerator has s = 8.16 TeV with a boost of the centre-of-mass boundary defining the sidebands used in the calculation is var- corresponding to the p + Pb system, and the denominator has en- ied independently in order to understand the sensitivity of the Fig. 4. Summary of the relative sizes of major sources of systematic uncertainty in the cross-section measurement, as well as the combined uncertainty (excluding luminosity), γ shown as a function of photon transverse energy E T . The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 235 measurement to the double sideband binning and correlation as- reflects a conservative difference compared with the default esti- sumptions. The dominant uncertainty arises from uncertainty in mate of this fraction of about 50–80% from the MC samples. This the level of sideband correlation. This is estimated directly from variation gives a relative change in the cross-section of approxi- data by dividing the non-isolated region in two subregions and mately 1% for all kinematic regions, which is taken as a systematic calculating the ratio of identified to background-enhanced yields uncertainty. The uncertainty in the integrated luminosity of the in each subregion. These ratios differ at the level of 10% which combined data sample is 2.4% It is derived, following a method- agrees with estimates from previous studies [10]. This ±10% vari- ology similar to that detailed in Ref. [42], and using the LUCID-2 ation in the sideband correlation yields a 13% uncertainty in the detector for the baseline luminosity measurements [43], from cali- γ cross-section in the lowest E T range, decreasing to less than 1% bration of the luminosity scale using x-y beam-separation scans. γ for E T > 100 GeV. The inverted photon identification requirement for the background candidates is varied to be less or more re- 6.2. R pPb uncertainty strictive about which shower shapes the background candidates are required to fail. This variation yields an uncertainty that is The nuclear modification factor R pPb is affected by systematic γ less than 1% for all E T in the forward and backward rapidity uncertainties associated with the p + Pb and pp measurements. bins, but is significant at mid-rapidity (−1.84 < η∗ < 0.91) where The uncertainties in the differential cross-section of the pp refer- γ it is 9% in the lowest E T bin and decreases to be less than 1% ence data are obtained directly from Ref. [9]. Due to differences γ for E T > 100 GeV. Variations in the isolation energy threshold of in photon reconstruction, energy calibration, isolation and iden- ±1 GeV have been shown to cover any difference between simula- tification procedures between the pp and p + Pb datasets, the tions and data [10]. These variations result in a 1–2% effect on the uncertainties are treated as uncorrelated and added in quadrature. γ γ γ cross-section in the lowest E T range and less than 1% at higher E T . The uncertainty in the extrapolation of the pp E T spectrum The uncertainty associated with the inverted shower-shape was at 8 TeV is determined by using an alternative method to derive smoothed and symmetrised, however, the other uncertainties are the multiplicative extrapolation factors. Instead of Jetphox, photon √ derived asymmetrically from the positive and negative variations cross-sections for the 8 TeV and rapidity-boosted s = 8.16 TeV separately. kinematics are determined from Pythia 8. The extrapolation factors Uncertainties associated with detector performance corrections from both Jetphox and Pythia 8 are shown in Fig. 3. Additionally, γ are dominant at high E T . A detailed description of the several Jetphox is run with an alternative PDF set to quantify the impact components of the photon energy scale and resolution uncertain- of a given PDF choice. The differences between the extrapolation ties are given in Ref. [10]. The impact of these on the measurement factors from these two variations, which are at most a few per- γ is determined by varying the reconstructed photon E T in simula- cent in the kinematic region of the measurement and subdominant tion within the energy scale uncertainties and deriving alternative with respect to the other uncertainties in the cross-sections, are correction factors for positive and negative variations separately. Of added in quadrature and used as an estimate of the uncertainty in these, the impact of the energy scale variation is dominant, giving the extrapolation procedure. a 10–15% contribution at 500 GeV in the forward and backward For the measurement of the ratio of R pPb values (Eq. (1)) be- γ regions, decreasing to less than 2% at the lowest E T . In the mid- tween the forward and backward pseudorapidity regions, each sys- rapidity region, the energy scale variation gives a 5% uncertainty at tematic variation affecting the purity and detector performance γ γ high E T , decreasing to less than 1% at low E T . Additionally, there corrections is applied to the numerator and denominator in a co- are uncertainties associated with corrections for small differences herent way, allowing them to partially cancel out in the ratio. All in reconstruction, identification and isolation efficiencies observed uncertainties in the other categories, except those from electron between data and simulation [31]. These uncertainties are about contamination and the beam direction difference, are treated as γ 5% in the forward regions and low E T and less than 2% elsewhere. correlated. For this reason, they cancel out; notably the p + Pb lu- Systematic uncertainties related to modelling in simulation, lu- minosity and pp cross-section uncertainties cancel out completely. minosity, electron contamination, and other sources tend to be The extrapolation uncertainties are treated as independent and are lower than those previously discussed. However, their combined added in quadrature to the other uncertainties in R pPb . effect is dominant in the mid-rapidity region and between 90 GeV The resulting uncertainty ranges from about 5% at the lowest and 250 GeV. To test the sensitivity of the measurement to the γ E T , where it is dominated by the uncertainty in the purity, to difference of isolation energy between particle-level and detector γ γ about 3% at mid-E T , and again about 5% at high E T , where it is level in the simulation, the generator-level isolation definition is dominated by uncertainty in the energy scale. A summary of the changed to better correspond to the reconstruction-level definition. uncertainties in the forward-to-backward ratio is shown in Fig. 5. The relative change in the cross-section after this deviation from γ the nominal is about 2% at low E T , decreasing to about 1% at high γ 7. Results E T , for each pseudorapidity region, and is taken as a symmetric uncertainty. An uncertainty is assigned to cover the possible con- Photon production cross-sections are shown in Fig. 6 for pho- tribution of misreconstructed electrons, primarily from the decays γ of W ± and Z bosons, to the selected photon yield. Based on sim- tons with E T > 20 GeV in three pseudorapidity regions. The mea- γ ulation studies, and the results of previous measurements [9,10], sured dσ /dE T values decrease by five orders of magnitude over γ γ γ this is assigned to be 1.3% for E T < 105 GeV in forward pseudo- the complete E T range, which extends out to E T ≈ 500 GeV for rapidity regions, and 0.5% everywhere else. To test the beam ori- photons at mid-rapidity. In Pythia 8, photons in this range typi- entation dependence, the cross-section is measured using the data cally arise from parton configurations in which the parton in the from each beam configuration separately. The two measurements nucleus has Bjorken scale variable, xA , in the range 3 × 10−3  agree at the level of 1%, well above the statistical uncertainty for xA  4 × 10−1 . In the nuclear modified PDF (nPDF) picture, this γ most E T bins. This difference is taken as a global, symmetric un- range probes the so-called shadowing (suppression for xA  0.1), certainty in the combined results. To test the sensitivity to the anti-shadowing (enhancement for 0.1  xA  0.3), and EMC (sup- relative fractions of direct and fragmentation photons in the MC pression for 0.3  xA  0.7) regions [24]. samples, the simulation is weighted such that the fraction of direct The data are compared with an NLO pQCD calculation similar photons is unity, that is, all photons in the sample are direct. This to that used in Ref. [3], where the data is similarly underestimated 236 The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 tions to the cross-section. The BFG set II [45] of parton-to-photon fragmentation functions are used, the number of massless quark flavours is set to five, and the renormalisation, factorisation and γ fragmentation scales are chosen to be E T . In addition to the cal- culation with the free-nucleon PDFs, separate calculations are per- formed with the EPPS16 [24] and nCTEQ15 [25] nPDF sets. The EPPS16 calculation uses the same free-proton PDF set, CT14, as the free-nucleon baseline to which the modifications are applied. The prediction is systematically lower than the data by up to 20% at γ γ low E T but is closer to the data at higher E T , consistent with the results of such comparisons in pp collisions at LHC energies [9,10]. A recent calculation of isolated photon production at NNLO found that the predicted cross-sections were systematically larger at low γ E T than the NLO prediction [46], and thus may provide a better description of the data in this and previous measurements. Uncertainties associated with these calculations are assessed in Fig. 5. Summary of the relative size of major sources of systematic uncertainty in a number of ways. Factorisation, renormalisation, and fragmenta- the forward-to-backward ratio of the nuclear modification factor R pPb , as well as tion scales are varied, up and down, by a factor of two as in γ the combined uncertainty, shown as a function of photon transverse energy E T . Ref. [9]. The uncertainty is taken as the envelope formed by the The Reference extrapolation refers to the uncertainty related to the extrapolation of the previously measured 8 TeV pp spectrum to 8.16 TeV and boosted kinematics. minimum and maximum of each variation in every kinematic re- gion and is dominant in most regions. PDF uncertainties are cal- culated via the standard CT14 error sets and correspond to a 68% at low ET, but using the updated CT14 [44] PDF set for the free- confidence interval. Again following Ref. [9] the sensitivity to the nucleon parton densities. Jetphox [23] is used to perform a full choice of αS is evaluated by varying αS by ±0.002 around the cen- NLO pQCD calculation of the direct and fragmentation contribu- tral value of 0.118 in the calculation and PDF. Uncertainties from γ Fig. 6. Prompt, isolated photon cross-sections as a function of transverse energy E T , shown for different centre-of-mass pseudorapidity, η∗ , regions in each panel. The data are compared with Jetphox with the EPPS16 nuclear PDF set [24], with the ratio of theory to data shown in the lower panels. Yellow bands correspond to total systematic uncertainties in the data (not including the luminosity uncertainty), vertical bars correspond to the statistical uncertainties in the data, and the red bands correspond to the uncertainties in the theoretical calculation. The green box (at the far right) represents the 2.4% luminosity uncertainty. Fig. 7. A breakdown of all systematic uncertainties in the cross-section prediction from Jetphox with the EPPS16 nPDF set. The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 237 γ Fig. 8. Nuclear modification factor R pPb for isolated, prompt photons as a function of photon transverse energy E T , shown for different centre-of-mass pseudorapidity, η∗ , √ regions in each panel. The R pPb is measured using a reference which is a simulation-derived extrapolation from s = 8 TeV pp data (see text). The data are identical in each row, but show comparisons with the expectations based on Jetphox with the EPPS16 nuclear PDF set (top) [24], with the nCTEQ15 nuclear PDF set (middle) [25], and with an initial-state energy-loss calculation (bottom) [4,5,26]. In all plots, the yellow bands and vertical bars correspond to total systematic and statistical uncertainties in the data respectively. In the top and middle panels, the red and purple bands correspond to the systematic uncertainties in the theoretical calculations. The green box (at the far right) represents the combined 2.4% p + Pb and 1.9% pp luminosity uncertainties. nPDFs are calculated from the error sets which correspond to 90% anti-shadowing regions. At mid-rapidity, nuclear effects are simi- γ γ confidence intervals, as described in Ref. [24]. These are converted larly small and consistent with unity at low E T , but at higher E T , into uncertainty bands which correspond to a 68% confidence in- there is a hint that R pPb is lower. This feature primarily reflects terval. A summary of each variation is shown in Fig. 7. the different up- and down-quark composition of the nucleus rela- Fig. 8 shows the nuclear modification factor R pPb as a func- tive to the proton and is more important at larger parton x. In this γ tion of E T in different η∗ regions. At forward rapidities (1.09 < case, the larger relative down-quark density decreases the photon ∗ η < 1.90), the R pPb value is consistent with unity, indicating that yield. This effect is evident in the Jetphox theory curve in blue nuclear effects are small. In Pythia 8, photons in this region typ- dash-dotted line, which includes the proton–neutron asymmetry ically arise from configurations with gluon partons from the Pb and the free-nucleon PDF set CT14. This effect is most pronounced nucleus with xA ≈ 10−2 . Nuclear modification pulls the pQCD cal- at backward pseudorapidity where, in Pythia 8, the nuclear parton γ culation down slightly for E T < 100 GeV, above which the mod- composition is typically a quark with xA ≈ 0.2. Here, nPDF modifi- ification reverses, indicating a crossover between shadowing and cation moves R pPb above the free-nucleon PDF calculation at low 238 The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 Fig. 9. Ratio of the nuclear modification factor R pPb between forward and backward pseudorapidity for isolated, prompt photons as a function of photon transverse energy γ E T . The data are identical in each panel, but show comparisons with the expectations based on Jetphox with the EPPS16 nuclear PDF set (top, left) [24] or with the nCTEQ15 nuclear PDF set (top, right) [25], and with an initial-state energy-loss calculation (bottom) [4,5,26]. The strength of the initial-state energy-loss effect is parameterised by λq , which represents the mean free path of partons in the nuclear medium and is smaller for a larger degree of energy loss. In all plots, the yellow bands and vertical bars correspond to total systematic and statistical uncertainties in the data respectively. In the left and right panels, the red and purple bands correspond to the systematic uncertainties in the calculations. γ γ γ E T but below at high E T , indicating the crossover from the anti- E T ≈ 100 GeV, this corresponds roughly to the ratio of R pPb from shadowing to the EMC region. photons from gluon nuclear parton configurations in the shadow- The R pPb calculations including nPDFs consider only the nPDF ing xA region to that from quark partons in the anti-shadowing uncertainty, since previous calculations have shown that the scale region. This can be seen in the top two panels of Fig. 9, where the and PDF uncertainties cancel out almost completely in the kine- nuclear modification (red/purple bands) brings the Jetphox calcu- matic region of the measurement [3], and no non-perturbative lation below that of the free-nucleon PDF (blue curve), though the corrections are applied. Within the present uncertainties, the data effect from EPPS16 is less significant. In contrast, the behaviour is γ are consistent with both the free-proton PDFs and with the small reversed at higher E T where the numerator probes the shadow- effects expected from a nuclear modification of the parton densi- ing/anti-shadowing crossover region and the denominator moves ties. deeper into the EMC region [24]. The data are consistent with The R pPb measurements are also compared with an initial-state the pQCD calculation before incorporating nuclear effects, except γ possibly in the region E T < 55 GeV, which is sensitive to the energy-loss prediction that is calculated within the framework de- γ scribed in Refs. [4,5,24]. In this model, the energetic partons un- effects from gluon shadowing. At low E T , the data are systemati- dergo multiple scattering in the cold nuclear medium, and thus cally higher than the calculations which incorporate nPDF effects, lose energy due to this medium-induced gluon bremsstrahlung, but approximately within their theoretical uncertainty. Addition- ally, in the lower plot of Fig. 9, the forward-to-backward ratios are before the hard collision. The calculation is performed with a compared with predictions from a model incorporating initial-state parton–gluon momentum transfer μ = 0.35 GeV and mean free energy loss. The data show a preference for no or only a limited path for quarks λq = 1.5 fm. Alternative calculations with a shorter amount of energy loss. path length (λq = 1 fm), and a control version with no initial-state energy loss, are also considered. The data disfavour a large sup- 8. Conclusion pression of the cross-section from initial-state energy-loss effects. The ratio of the R pPb values between forward and backward This letter presents a measurement of the inclusive prompt, √ pseudorapidity, shown in Fig. 9, is studied as a way to reduce isolated photon cross-section in p + Pb collisions at sNN = the effect of common systematic uncertainties and better isolate 8.16 TeV, using a dataset corresponding to an integrated luminos- the magnitude of nuclear effects [47]. The remaining systematic ity of 165 nb−1 recorded by the ATLAS experiment at the LHC. uncertainty, discussed in Sec. 6.2, is dominated by the reference The differential cross-section as a function of the photon trans- extrapolation and treated as uncorrelated between points. 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Battaglia 143 , M. Bauce 70a,70b , F. Bauer 142 , K.T. Bauer 168 , H.S. Bawa 150 , J.B. Beacham 123 , T. Beau 133 , P.H. Beauchemin 167 , P. Bechtle 24 , H.C. Beck 51 , H.P. Beck 20,r , K. Becker 50 , M. Becker 97 , C. Becot 44 , A. Beddall 12d , A.J. Beddall 12a , V.A. Bednyakov 77 , M. Bedognetti 118 , C.P. Bee 152 , T.A. Beermann 74 , M. Begalli 78b , M. Begel 26b , A. Behera 152 , J.K. Behr 44 , F. Beisiegel 24 , A.S. Bell 92 , G. Bella 158 , L. Bellagamba 23b , A. Bellerive 33 , M. Bellomo 157 , P. Bellos 9 , K. Belotskiy 110 , N.L. Belyaev 110 , The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 241 O. Benary 158,∗ , D. Benchekroun 34a , M. Bender 112 , N. Benekos 10 , Y. Benhammou 158 , E. Benhar Noccioli 180 , J. Benitez 75 , D.P. Benjamin 6 , M. Benoit 52 , J.R. Bensinger 27 , S. Bentvelsen 118 , L. Beresford 132 , M. Beretta 49 , D. Berge 44 , E. Bergeaas Kuutmann 169 , N. Berger 5 , B. Bergmann 139 , L.J. Bergsten 27 , J. Beringer 18 , S. Berlendis 7 , N.R. Bernard 100 , G. Bernardi 133 , C. Bernius 150 , F.U. Bernlochner 24 , T. Berry 91 , P. Berta 97 , C. Bertella 15a , G. Bertoli 43a,43b , I.A. Bertram 87 , G.J. Besjes 39 , O. Bessidskaia Bylund 179 , M. Bessner 44 , N. Besson 142 , A. Bethani 98 , S. Bethke 113 , A. Betti 24 , A.J. Bevan 90 , J. Beyer 113 , R. Bi 136 , R.M. Bianchi 136 , O. Biebel 112 , D. Biedermann 19 , R. Bielski 35 , K. Bierwagen 97 , N.V. Biesuz 69a,69b , M. Biglietti 72a , T.R.V. Billoud 107 , M. Bindi 51 , A. Bingul 12d , C. Bini 70a,70b , S. Biondi 23b,23a , M. Birman 177 , T. Bisanz 51 , J.P. Biswal 158 , C. Bittrich 46 , D.M. Bjergaard 47 , J.E. Black 150 , K.M. Black 25 , T. Blazek 29a , I. Bloch 44 , C. Blocker 27 , A. Blue 55 , U. Blumenschein 90 , Dr. Blunier 144a , G.J. Bobbink 118 , V.S. Bobrovnikov 120b,120a , S.S. Bocchetta 94 , A. Bocci 47 , D. Boerner 179 , D. Bogavac 112 , A.G. Bogdanchikov 120b,120a , C. Bohm 43a , V. Boisvert 91 , P. Bokan 51,169 , T. Bold 81a , A.S. Boldyrev 111 , A.E. Bolz 59b , M. Bomben 133 , M. Bona 90 , J.S. Bonilla 128 , M. Boonekamp 142 , H.M. Borecka-Bielska 88 , A. Borisov 121 , G. Borissov 87 , J. Bortfeldt 35 , D. Bortoletto 132 , V. Bortolotto 71a,71b , D. Boscherini 23b , M. Bosman 14 , J.D. Bossio Sola 30 , K. Bouaouda 34a , J. Boudreau 136 , E.V. Bouhova-Thacker 87 , D. Boumediene 37 , C. Bourdarios 129 , S.K. Boutle 55 , A. Boveia 123 , J. Boyd 35 , D. Boye 32b,ap , I.R. Boyko 77 , A.J. Bozson 91 , J. Bracinik 21 , N. Brahimi 99 , A. Brandt 8 , G. Brandt 179 , O. Brandt 59a , F. Braren 44 , U. Bratzler 161 , B. Brau 100 , J.E. Brau 128 , W.D. Breaden Madden 55 , K. Brendlinger 44 , L. Brenner 44 , R. Brenner 169 , S. Bressler 177 , B. Brickwedde 97 , D.L. Briglin 21 , D. Britton 55 , D. Britzger 113 , I. Brock 24 , R. Brock 104 , G. Brooijmans 38 , T. Brooks 91 , W.K. Brooks 144b , E. Brost 119 , J.H Broughton 21 , P.A. Bruckman de Renstrom 82 , D. Bruncko 29b , A. Bruni 23b , G. Bruni 23b , L.S. Bruni 118 , S. Bruno 71a,71b , B.H. Brunt 31 , M. Bruschi 23b , N. Bruscino 136 , P. Bryant 36 , L. Bryngemark 94 , T. Buanes 17 , Q. Buat 35 , P. Buchholz 148 , A.G. Buckley 55 , I.A. Budagov 77 , M.K. Bugge 131 , F. Bührer 50 , O. Bulekov 110 , D. Bullock 8 , T.J. Burch 119 , S. Burdin 88 , C.D. Burgard 118 , A.M. Burger 5 , B. Burghgrave 8 , K. Burka 82 , S. Burke 141 , I. Burmeister 45 , J.T.P. Burr 132 , V. Büscher 97 , E. Buschmann 51 , P. Bussey 55 , J.M. Butler 25 , C.M. Buttar 55 , J.M. Butterworth 92 , P. Butti 35 , W. Buttinger 35 , A. Buzatu 155 , A.R. Buzykaev 120b,120a , G. Cabras 23b,23a , S. Cabrera Urbán 171 , D. Caforio 139 , H. Cai 170 , V.M.M. Cairo 2 , O. Cakir 4a , N. Calace 35 , P. Calafiura 18 , A. Calandri 99 , G. Calderini 133 , P. Calfayan 63 , G. Callea 55 , L.P. Caloba 78b , S. Calvente Lopez 96 , D. Calvet 37 , S. Calvet 37 , T.P. Calvet 152 , M. Calvetti 69a,69b , R. Camacho Toro 133 , S. Camarda 35 , D. Camarero Munoz 96 , P. Camarri 71a,71b , D. Cameron 131 , R. Caminal Armadans 100 , C. Camincher 35 , S. Campana 35 , M. Campanelli 92 , A. Camplani 39 , A. Campoverde 148 , V. Canale 67a,67b , M. Cano Bret 58c , J. Cantero 126 , T. Cao 158 , Y. Cao 170 , M.D.M. Capeans Garrido 35 , M. Capua 40b,40a , R.M. Carbone 38 , R. Cardarelli 71a , F.C. Cardillo 146 , I. Carli 140 , T. Carli 35 , G. Carlino 67a , B.T. Carlson 136 , L. Carminati 66a,66b , R.M.D. Carney 43a,43b , S. Caron 117 , E. Carquin 144b , S. Carrá 66a,66b , J.W.S. Carter 164 , D. Casadei 32b , M.P. Casado 14,g , A.F. Casha 164 , D.W. Casper 168 , R. Castelijn 118 , F.L. Castillo 171 , V. Castillo Gimenez 171 , N.F. Castro 137a,137e , A. Catinaccio 35 , J.R. Catmore 131 , A. Cattai 35 , J. Caudron 24 , V. Cavaliere 26b , E. Cavallaro 14 , D. Cavalli 66a , M. Cavalli-Sforza 14 , V. Cavasinni 69a,69b , E. Celebi 12b , F. Ceradini 72a,72b , L. Cerda Alberich 171 , A.S. Cerqueira 78a , A. Cerri 153 , L. Cerrito 71a,71b , F. Cerutti 18 , A. Cervelli 23b,23a , S.A. Cetin 12b , A. Chafaq 34a , D. Chakraborty 119 , S.K. Chan 57 , W.S. Chan 118 , W.Y. Chan 88 , J.D. Chapman 31 , B. Chargeishvili 156b , D.G. Charlton 21 , C.C. Chau 33 , C.A. Chavez Barajas 153 , S. Che 123 , A. Chegwidden 104 , S. Chekanov 6 , S.V. Chekulaev 165a , G.A. Chelkov 77,au , M.A. Chelstowska 35 , B. Chen 76 , C. Chen 58a , C.H. Chen 76 , H. Chen 26b , J. Chen 58a , J. Chen 38 , S. Chen 134 , S.J. Chen 15c , X. Chen 15b,at , Y. Chen 80 , Y-H. Chen 44 , H.C. Cheng 61a , H.J. Cheng 15d , A. Cheplakov 77 , E. Cheremushkina 121 , R. Cherkaoui El Moursli 34e , E. Cheu 7 , K. Cheung 62 , T.J.A. Chevalérias 142 , L. Chevalier 142 , V. Chiarella 49 , G. Chiarelli 69a , G. Chiodini 65a , A.S. Chisholm 35,21 , A. Chitan 28b , I. Chiu 160 , Y.H. Chiu 173 , M.V. Chizhov 77 , K. Choi 63 , A.R. Chomont 129 , S. Chouridou 159 , Y.S. Chow 118 , V. Christodoulou 92 , M.C. Chu 61a , J. Chudoba 138 , A.J. Chuinard 101 , J.J. Chwastowski 82 , L. Chytka 127 , D. Cinca 45 , V. Cindro 89 , I.A. Cioară 24 , A. Ciocio 18 , F. Cirotto 67a,67b , Z.H. Citron 177 , M. Citterio 66a , A. Clark 52 , M.R. Clark 38 , P.J. Clark 48 , C. Clement 43a,43b , Y. Coadou 99 , M. Cobal 64a,64c , A. Coccaro 53b , J. Cochran 76 , H. Cohen 158 , A.E.C. Coimbra 177 , L. Colasurdo 117 , B. Cole 38 , A.P. Colijn 118 , J. Collot 56 , P. Conde Muiño 137a,h , E. Coniavitis 50 , S.H. Connell 32b , I.A. Connelly 98 , S. Constantinescu 28b , F. Conventi 67a,ax , 242 The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 A.M. Cooper-Sarkar 132 , F. Cormier 172 , K.J.R. Cormier 164 , L.D. Corpe 92 , M. Corradi 70a,70b , E.E. Corrigan 94 , F. Corriveau 101,ac , A. Cortes-Gonzalez 35 , M.J. Costa 171 , F. Costanza 5 , D. Costanzo 146 , G. Cottin 31 , G. Cowan 91 , J.W. Cowley 31 , B.E. Cox 98 , J. Crane 98 , K. Cranmer 122 , S.J. Crawley 55 , R.A. Creager 134 , G. Cree 33 , S. Crépé-Renaudin 56 , F. Crescioli 133 , M. Cristinziani 24 , V. Croft 122 , G. Crosetti 40b,40a , A. Cueto 96 , T. Cuhadar Donszelmann 146 , A.R. Cukierman 150 , S. Czekierda 82 , P. Czodrowski 35 , M.J. Da Cunha Sargedas De Sousa 58b , C. Da Via 98 , W. Dabrowski 81a , T. Dado 29a,x , S. Dahbi 34e , T. Dai 103 , F. Dallaire 107 , C. Dallapiccola 100 , M. Dam 39 , G. D’amen 23b,23a , J. Damp 97 , J.R. Dandoy 134 , M.F. Daneri 30 , N.P. Dang 178,k , N.D Dann 98 , M. Danninger 172 , V. Dao 35 , G. Darbo 53b , S. Darmora 8 , O. Dartsi 5 , A. Dattagupta 128 , T. Daubney 44 , S. D’Auria 66a,66b , W. Davey 24 , C. David 44 , T. Davidek 140 , D.R. Davis 47 , E. Dawe 102 , I. Dawson 146 , K. De 8 , R. De Asmundis 67a , A. De Benedetti 125 , M. De Beurs 118 , S. De Castro 23b,23a , S. De Cecco 70a,70b , N. De Groot 117 , P. de Jong 118 , H. De la Torre 104 , F. De Lorenzi 76 , A. De Maria 69a,69b , D. De Pedis 70a , A. De Salvo 70a , U. De Sanctis 71a,71b , M. De Santis 71a,71b , A. De Santo 153 , K. De Vasconcelos Corga 99 , J.B. De Vivie De Regie 129 , C. Debenedetti 143 , D.V. Dedovich 77 , N. Dehghanian 3 , M. Del Gaudio 40b,40a , J. Del Peso 96 , Y. Delabat Diaz 44 , D. Delgove 129 , F. Deliot 142 , C.M. Delitzsch 7 , M. Della Pietra 67a,67b , D. Della Volpe 52 , A. Dell’Acqua 35 , L. Dell’Asta 25 , M. Delmastro 5 , C. Delporte 129 , P.A. Delsart 56 , D.A. DeMarco 164 , S. Demers 180 , M. Demichev 77 , S.P. Denisov 121 , D. Denysiuk 118 , L. D’Eramo 133 , D. Derendarz 82 , J.E. Derkaoui 34d , F. Derue 133 , P. Dervan 88 , K. Desch 24 , C. Deterre 44 , K. Dette 164 , M.R. Devesa 30 , P.O. Deviveiros 35 , A. Dewhurst 141 , S. Dhaliwal 27 , F.A. Di Bello 52 , A. Di Ciaccio 71a,71b , L. Di Ciaccio 5 , W.K. Di Clemente 134 , C. Di Donato 67a,67b , A. Di Girolamo 35 , G. Di Gregorio 69a,69b , B. Di Micco 72a,72b , R. Di Nardo 100 , K.F. Di Petrillo 57 , R. Di Sipio 164 , D. Di Valentino 33 , C. Diaconu 99 , M. Diamond 164 , F.A. Dias 39 , T. Dias Do Vale 137a , M.A. Diaz 144a , J. Dickinson 18 , E.B. Diehl 103 , J. Dietrich 19 , S. Díez Cornell 44 , A. Dimitrievska 18 , J. Dingfelder 24 , F. Dittus 35 , F. Djama 99 , T. Djobava 156b , J.I. Djuvsland 17 , M.A.B. Do Vale 78c , M. Dobre 28b , D. Dodsworth 27 , C. Doglioni 94 , J. Dolejsi 140 , Z. Dolezal 140 , M. Donadelli 78d , J. Donini 37 , A. D’onofrio 90 , M. D’Onofrio 88 , J. Dopke 141 , A. Doria 67a , M.T. Dova 86 , A.T. Doyle 55 , E. Drechsler 149 , E. Dreyer 149 , T. Dreyer 51 , Y. Du 58b , F. Dubinin 108 , M. Dubovsky 29a , A. Dubreuil 52 , E. Duchovni 177 , G. Duckeck 112 , A. Ducourthial 133 , O.A. Ducu 107,w , D. Duda 113 , A. Dudarev 35 , A.C. Dudder 97 , E.M. Duffield 18 , L. Duflot 129 , M. Dührssen 35 , C. Dülsen 179 , M. Dumancic 177 , A.E. Dumitriu 28b,e , A.K. Duncan 55 , M. Dunford 59a , A. Duperrin 99 , H. Duran Yildiz 4a , M. Düren 54 , A. Durglishvili 156b , D. Duschinger 46 , B. Dutta 44 , D. Duvnjak 1 , G. Dyckes 134 , M. Dyndal 44 , S. Dysch 98 , B.S. Dziedzic 82 , K.M. Ecker 113 , R.C. Edgar 103 , T. Eifert 35 , G. Eigen 17 , K. Einsweiler 18 , T. Ekelof 169 , M. El Kacimi 34c , R. El Kosseifi 99 , V. Ellajosyula 99 , M. Ellert 169 , F. Ellinghaus 179 , A.A. Elliot 90 , N. Ellis 35 , J. Elmsheuser 26b , M. Elsing 35 , D. Emeliyanov 141 , A. Emerman 38 , Y. Enari 160 , J.S. Ennis 175 , M.B. Epland 47 , J. Erdmann 45 , A. Ereditato 20 , S. Errede 170 , M. Escalier 129 , C. Escobar 171 , O. Estrada Pastor 171 , A.I. Etienvre 142 , E. Etzion 158 , H. Evans 63 , A. Ezhilov 135 , M. Ezzi 34e , F. Fabbri 55 , L. Fabbri 23b,23a , V. Fabiani 117 , G. Facini 92 , R.M. Faisca Rodrigues Pereira 137a , R.M. Fakhrutdinov 121 , S. Falciano 70a , P.J. Falke 5 , S. Falke 5 , J. Faltova 140 , Y. Fang 15a , M. Fanti 66a,66b , A. Farbin 8 , A. Farilla 72a , E.M. Farina 68a,68b , T. Farooque 104 , S. Farrell 18 , S.M. Farrington 175 , P. Farthouat 35 , F. Fassi 34e , P. Fassnacht 35 , D. Fassouliotis 9 , M. Faucci Giannelli 48 , W.J. Fawcett 31 , L. Fayard 129 , O.L. Fedin 135,p , W. Fedorko 172 , M. Feickert 41 , S. Feigl 131 , L. Feligioni 99 , C. Feng 58b , E.J. Feng 35 , M. Feng 47 , M.J. Fenton 55 , A.B. Fenyuk 121 , J. Ferrando 44 , A. Ferrari 169 , P. Ferrari 118 , R. Ferrari 68a , D.E. Ferreira de Lima 59b , A. Ferrer 171 , D. Ferrere 52 , C. Ferretti 103 , F. Fiedler 97 , A. Filipčič 89 , F. Filthaut 117 , K.D. Finelli 25 , M.C.N. Fiolhais 137a,137c,a , L. Fiorini 171 , C. Fischer 14 , W.C. Fisher 104 , N. Flaschel 44 , I. Fleck 148 , P. Fleischmann 103 , R.R.M. Fletcher 134 , T. Flick 179 , B.M. Flierl 112 , L.M. Flores 134 , L.R. Flores Castillo 61a , F.M. Follega 73a,73b , N. Fomin 17 , G.T. Forcolin 73a,73b , A. Formica 142 , F.A. Förster 14 , A.C. Forti 98 , A.G. Foster 21 , D. Fournier 129 , H. Fox 87 , S. Fracchia 146 , P. Francavilla 69a,69b , M. Franchini 23b,23a , S. Franchino 59a , D. Francis 35 , L. Franconi 143 , M. Franklin 57 , M. Frate 168 , A.N. Fray 90 , D. Freeborn 92 , B. Freund 107 , W.S. Freund 78b , E.M. Freundlich 45 , D.C. Frizzell 125 , D. Froidevaux 35 , J.A. Frost 132 , C. Fukunaga 161 , E. Fullana Torregrosa 171 , E. Fumagalli 53b,53a , T. Fusayasu 114 , J. Fuster 171 , O. Gabizon 157 , A. Gabrielli 23b,23a , A. Gabrielli 18 , G.P. Gach 81a , S. Gadatsch 52 , P. Gadow 113 , G. Gagliardi 53b,53a , L.G. Gagnon 107 , C. Galea 28b , B. Galhardo 137a,137c , E.J. Gallas 132 , B.J. Gallop 141 , P. Gallus 139 , G. Galster 39 , R. Gamboa Goni 90 , K.K. Gan 123 , S. Ganguly 177 , J. Gao 58a , Y. Gao 88 , The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 243 Y.S. Gao 150,m , C. García 171 , J.E. García Navarro 171 , J.A. García Pascual 15a , C. Garcia-Argos 50 , M. Garcia-Sciveres 18 , R.W. Gardner 36 , N. Garelli 150 , S. Gargiulo 50 , V. Garonne 131 , K. Gasnikova 44 , A. Gaudiello 53b,53a , G. Gaudio 68a , I.L. Gavrilenko 108 , A. Gavrilyuk 109 , C. Gay 172 , G. Gaycken 24 , E.N. Gazis 10 , C.N.P. Gee 141 , J. Geisen 51 , M. Geisen 97 , M.P. Geisler 59a , C. Gemme 53b , M.H. Genest 56 , C. Geng 103 , S. Gentile 70a,70b , S. George 91 , D. Gerbaudo 14 , G. Gessner 45 , S. Ghasemi 148 , M. Ghasemi Bostanabad 173 , M. Ghneimat 24 , B. Giacobbe 23b , S. Giagu 70a,70b , N. Giangiacomi 23b,23a , P. Giannetti 69a , A. Giannini 67a,67b , S.M. Gibson 91 , M. Gignac 143 , D. Gillberg 33 , G. Gilles 179 , D.M. Gingrich 3,av , M.P. Giordani 64a,64c , F.M. Giorgi 23b , P.F. Giraud 142 , P. Giromini 57 , G. Giugliarelli 64a,64c , D. Giugni 66a , F. Giuli 132 , M. Giulini 59b , S. Gkaitatzis 159 , I. Gkialas 9,j , E.L. Gkougkousis 14 , P. Gkountoumis 10 , L.K. Gladilin 111 , C. Glasman 96 , J. Glatzer 14 , P.C.F. Glaysher 44 , A. Glazov 44 , M. Goblirsch-Kolb 27 , S. Goldfarb 102 , T. Golling 52 , D. Golubkov 121 , A. Gomes 137a,137b , R. Goncalves Gama 51 , R. Gonçalo 137a , G. Gonella 50 , L. Gonella 21 , A. Gongadze 77 , F. Gonnella 21 , J.L. Gonski 57 , S. González de la Hoz 171 , S. Gonzalez-Sevilla 52 , L. Goossens 35 , P.A. Gorbounov 109 , H.A. Gordon 26b , B. Gorini 35 , E. Gorini 65a,65b , A. Gorišek 89 , A.T. Goshaw 47 , C. Gössling 45 , M.I. Gostkin 77 , C.A. Gottardo 24 , C.R. Goudet 129 , D. Goujdami 34c , A.G. Goussiou 145 , N. Govender 32b,c , C. Goy 5 , E. Gozani 157 , I. Grabowska-Bold 81a , P.O.J. Gradin 169 , E.C. Graham 88 , J. Gramling 168 , E. Gramstad 131 , S. Grancagnolo 19 , V. Gratchev 135 , P.M. Gravila 28f , F.G. Gravili 65a,65b , C. Gray 55 , H.M. Gray 18 , Z.D. Greenwood 93,ak , C. Grefe 24 , K. Gregersen 94 , I.M. Gregor 44 , P. Grenier 150 , K. Grevtsov 44 , N.A. Grieser 125 , J. Griffiths 8 , A.A. Grillo 143 , K. Grimm 150,b , S. Grinstein 14,y , Ph. Gris 37 , J.-F. Grivaz 129 , S. Groh 97 , E. Gross 177 , J. Grosse-Knetter 51 , G.C. Grossi 93 , Z.J. Grout 92 , C. Grud 103 , A. Grummer 116 , L. Guan 103 , W. Guan 178 , J. Guenther 35 , A. Guerguichon 129 , F. Guescini 165a , D. Guest 168 , R. Gugel 50 , B. Gui 123 , T. Guillemin 5 , S. Guindon 35 , U. Gul 55 , J. Guo 58c , W. Guo 103 , Y. Guo 58a,s , Z. Guo 99 , R. Gupta 44 , S. Gurbuz 12c , G. Gustavino 125 , P. Gutierrez 125 , C. Gutschow 92 , C. Guyot 142 , M.P. Guzik 81a , C. Gwenlan 132 , C.B. Gwilliam 88 , A. Haas 122 , C. Haber 18 , H.K. Hadavand 8 , N. Haddad 34e , A. Hadef 58a , S. Hageböck 24 , M. Hagihara 166 , M. Haleem 174 , J. Haley 126 , G. Halladjian 104 , G.D. Hallewell 99 , K. Hamacher 179 , P. Hamal 127 , K. Hamano 173 , A. Hamilton 32a , G.N. Hamity 146 , K. Han 58a,aj , L. Han 58a , S. Han 15d , K. Hanagaki 79,u , M. Hance 143 , D.M. Handl 112 , B. Haney 134 , R. Hankache 133 , P. Hanke 59a , E. Hansen 94 , J.B. Hansen 39 , J.D. Hansen 39 , M.C. Hansen 24 , P.H. Hansen 39 , E.C. Hanson 98 , K. Hara 166 , A.S. Hard 178 , T. Harenberg 179 , S. Harkusha 105 , P.F. Harrison 175 , N.M. Hartmann 112 , Y. Hasegawa 147 , A. Hasib 48 , S. Hassani 142 , S. Haug 20 , R. Hauser 104 , L. Hauswald 46 , L.B. Havener 38 , M. Havranek 139 , C.M. Hawkes 21 , R.J. Hawkings 35 , D. Hayden 104 , C. Hayes 152 , C.P. Hays 132 , J.M. Hays 90 , H.S. Hayward 88 , S.J. Haywood 141 , F. He 58a , M.P. Heath 48 , V. Hedberg 94 , L. Heelan 8 , S. Heer 24 , K.K. Heidegger 50 , J. Heilman 33 , S. Heim 44 , T. Heim 18 , B. Heinemann 44,aq , J.J. Heinrich 112 , L. Heinrich 122 , C. Heinz 54 , J. Hejbal 138 , L. Helary 35 , A. Held 172 , S. Hellesund 131 , C.M. Helling 143 , S. Hellman 43a,43b , C. Helsens 35 , R.C.W. Henderson 87 , Y. Heng 178 , S. Henkelmann 172 , A.M. Henriques Correia 35 , G.H. Herbert 19 , H. Herde 27 , V. Herget 174 , Y. Hernández Jiménez 32c , H. Herr 97 , M.G. Herrmann 112 , T. Herrmann 46 , G. Herten 50 , R. Hertenberger 112 , L. Hervas 35 , T.C. Herwig 134 , G.G. Hesketh 92 , N.P. Hessey 165a , A. Higashida 160 , S. Higashino 79 , E. Higón-Rodriguez 171 , K. Hildebrand 36 , E. Hill 173 , J.C. Hill 31 , K.K. Hill 26b , K.H. Hiller 44 , S.J. Hillier 21 , M. Hils 46 , I. Hinchliffe 18 , F. Hinterkeuser 24 , M. Hirose 130 , D. Hirschbuehl 179 , B. Hiti 89 , O. Hladik 138 , D.R. Hlaluku 32c , X. Hoad 48 , J. Hobbs 152 , N. Hod 165a , M.C. Hodgkinson 146 , A. Hoecker 35 , M.R. Hoeferkamp 116 , F. Hoenig 112 , D. Hohn 50 , D. Hohov 129 , T.R. Holmes 36 , M. Holzbock 112 , M. Homann 45 , L.B.A.H Hommels 31 , S. Honda 166 , T. Honda 79 , T.M. Hong 136 , A. Hönle 113 , B.H. Hooberman 170 , W.H. Hopkins 128 , Y. Horii 115 , P. Horn 46 , A.J. Horton 149 , L.A. Horyn 36 , J-Y. Hostachy 56 , A. Hostiuc 145 , S. Hou 155 , A. Hoummada 34a , J. Howarth 98 , J. Hoya 86 , M. Hrabovsky 127 , J. Hrdinka 35 , I. Hristova 19 , J. Hrivnac 129 , A. Hrynevich 106 , T. Hryn’ova 5 , P.J. Hsu 62 , S.-C. Hsu 145 , Q. Hu 26b , S. Hu 58c , Y. Huang 15a , Z. Hubacek 139 , F. Hubaut 99 , M. Huebner 24 , F. Huegging 24 , T.B. Huffman 132 , M. Huhtinen 35 , R.F.H. Hunter 33 , P. Huo 152 , A.M. Hupe 33 , N. Huseynov 77,ae , J. Huston 104 , J. Huth 57 , R. Hyneman 103 , G. Iacobucci 52 , G. Iakovidis 26b , I. Ibragimov 148 , L. Iconomidou-Fayard 129 , Z. Idrissi 34e , P. Iengo 35 , R. Ignazzi 39 , O. Igonkina 118,aa , R. Iguchi 160 , T. Iizawa 52 , Y. Ikegami 79 , M. Ikeno 79 , D. Iliadis 159 , N. Ilic 117 , F. Iltzsche 46 , G. Introzzi 68a,68b , M. Iodice 72a , K. Iordanidou 38 , V. Ippolito 70a,70b , M.F. Isacson 169 , N. Ishijima 130 , M. Ishino 160 , M. Ishitsuka 162 , W. Islam 126 , C. Issever 132 , S. Istin 157 , F. Ito 166 , J.M. Iturbe Ponce 61a , 244 The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 R. Iuppa 73a,73b , A. Ivina 177 , H. Iwasaki 79 , J.M. Izen 42 , V. Izzo 67a , P. Jacka 138 , P. Jackson 1 , R.M. Jacobs 24 , V. Jain 2 , G. Jäkel 179 , K.B. Jakobi 97 , K. Jakobs 50 , S. Jakobsen 74 , T. Jakoubek 138 , D.O. Jamin 126 , R. Jansky 52 , J. Janssen 24 , M. Janus 51 , P.A. Janus 81a , G. Jarlskog 94 , N. Javadov 77,ae , T. Javůrek 35 , M. Javurkova 50 , F. Jeanneau 142 , L. Jeanty 18 , J. Jejelava 156a,af , A. Jelinskas 175 , P. Jenni 50,d , J. Jeong 44 , N. Jeong 44 , S. Jézéquel 5 , H. Ji 178 , J. Jia 152 , H. Jiang 76 , Y. Jiang 58a , Z. Jiang 150,q , S. Jiggins 50 , F.A. Jimenez Morales 37 , J. Jimenez Pena 171 , S. Jin 15c , A. Jinaru 28b , O. Jinnouchi 162 , H. Jivan 32c , P. Johansson 146 , K.A. Johns 7 , C.A. Johnson 63 , K. Jon-And 43a,43b , R.W.L. Jones 87 , S.D. Jones 153 , S. Jones 7 , T.J. Jones 88 , J. Jongmanns 59a , P.M. Jorge 137a,137b , J. Jovicevic 165a , X. Ju 18 , J.J. Junggeburth 113 , A. Juste Rozas 14,y , A. Kaczmarska 82 , M. Kado 129 , H. Kagan 123 , M. Kagan 150 , T. Kaji 176 , E. Kajomovitz 157 , C.W. Kalderon 94 , A. Kaluza 97 , S. Kama 41 , A. Kamenshchikov 121 , L. Kanjir 89 , Y. Kano 160 , V.A. Kantserov 110 , J. Kanzaki 79 , L.S. Kaplan 178 , D. Kar 32c , M.J. Kareem 165b , E. Karentzos 10 , S.N. Karpov 77 , Z.M. Karpova 77 , V. Kartvelishvili 87 , A.N. Karyukhin 121 , L. Kashif 178 , R.D. Kass 123 , A. Kastanas 43a,43b , Y. Kataoka 160 , C. Kato 58d,58c , J. Katzy 44 , K. Kawade 80 , K. Kawagoe 85 , T. Kawaguchi 115 , T. Kawamoto 160 , G. Kawamura 51 , E.F. Kay 88 , V.F. Kazanin 120b,120a , R. Keeler 173 , R. Kehoe 41 , J.S. Keller 33 , E. Kellermann 94 , J.J. Kempster 21 , J. Kendrick 21 , O. Kepka 138 , S. Kersten 179 , B.P. Kerševan 89 , S. Ketabchi Haghighat 164 , R.A. Keyes 101 , M. Khader 170 , F. Khalil-Zada 13 , A. Khanov 126 , A.G. Kharlamov 120b,120a , T. Kharlamova 120b,120a , E.E. Khoda 172 , A. Khodinov 163 , T.J. Khoo 52 , E. Khramov 77 , J. Khubua 156b , S. Kido 80 , M. Kiehn 52 , C.R. Kilby 91 , Y.K. Kim 36 , N. Kimura 64a,64c , O.M. Kind 19 , B.T. King 88 , D. Kirchmeier 46 , J. Kirk 141 , A.E. Kiryunin 113 , T. Kishimoto 160 , V. Kitali 44 , O. Kivernyk 5 , E. Kladiva 29b,∗ , T. Klapdor-Kleingrothaus 50 , M.H. Klein 103 , M. Klein 88 , U. Klein 88 , K. Kleinknecht 97 , P. Klimek 119 , A. Klimentov 26b , T. Klingl 24 , T. Klioutchnikova 35 , F.F. Klitzner 112 , P. Kluit 118 , S. Kluth 113 , E. Kneringer 74 , E.B.F.G. Knoops 99 , A. Knue 50 , A. Kobayashi 160 , D. Kobayashi 85 , T. Kobayashi 160 , M. Kobel 46 , M. Kocian 150 , P. Kodys 140 , P.T. Koenig 24 , T. Koffas 33 , E. Koffeman 118 , N.M. Köhler 113 , T. Koi 150 , M. Kolb 59b , I. Koletsou 5 , T. 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Kuehn 35 , A. Kugel 59a , T. Kuhl 44 , V. Kukhtin 77 , R. Kukla 99 , Y. Kulchitsky 105,ai , S. Kuleshov 144b , Y.P. Kulinich 170 , M. Kuna 56 , T. Kunigo 83 , A. Kupco 138 , T. Kupfer 45 , O. Kuprash 158 , H. Kurashige 80 , L.L. Kurchaninov 165a , Y.A. Kurochkin 105 , A. Kurova 110 , M.G. Kurth 15d , E.S. Kuwertz 35 , M. Kuze 162 , J. Kvita 127 , T. Kwan 101 , A. La Rosa 113 , J.L. La Rosa Navarro 78d , L. La Rotonda 40b,40a , F. La Ruffa 40b,40a , C. Lacasta 171 , F. Lacava 70a,70b , J. Lacey 44 , D.P.J. Lack 98 , H. Lacker 19 , D. Lacour 133 , E. Ladygin 77 , R. Lafaye 5 , B. Laforge 133 , T. Lagouri 32c , S. Lai 51 , S. Lammers 63 , W. Lampl 7 , E. Lançon 26b , U. Landgraf 50 , M.P.J. Landon 90 , M.C. Lanfermann 52 , V.S. Lang 44 , J.C. Lange 51 , R.J. Langenberg 35 , A.J. Lankford 168 , F. Lanni 26b , K. Lantzsch 24 , A. Lanza 68a , A. Lapertosa 53b,53a , S. Laplace 133 , J.F. Laporte 142 , T. Lari 66a , F. Lasagni Manghi 23b,23a , M. Lassnig 35 , T.S. Lau 61a , A. Laudrain 129 , M. Lavorgna 67a,67b , M. Lazzaroni 66a,66b , B. Le 102 , O. Le Dortz 133 , E. Le Guirriec 99 , E.P. Le Quilleuc 142 , M. LeBlanc 7 , T. LeCompte 6 , F. Ledroit-Guillon 56 , C.A. Lee 26b , G.R. Lee 144a , L. Lee 57 , S.C. Lee 155 , B. Lefebvre 101 , M. Lefebvre 173 , F. Legger 112 , C. Leggett 18 , K. Lehmann 149 , N. Lehmann 179 , G. Lehmann Miotto 35 , W.A. Leight 44 , A. Leisos 159,v , M.A.L. Leite 78d , R. Leitner 140 , D. Lellouch 177 , K.J.C. Leney 92 , T. Lenz 24 , B. Lenzi 35 , R. Leone 7 , S. Leone 69a , C. Leonidopoulos 48 , G. Lerner 153 , C. Leroy 107 , R. Les 164 , A.A.J. Lesage 142 , C.G. Lester 31 , M. Levchenko 135 , J. Levêque 5 , D. Levin 103 , L.J. Levinson 177 , D. Lewis 90 , B. Li 15b , B. Li 103 , C-Q. Li 58a,al , H. Li 58a , H. Li 58b , K. Li 150 , L. Li 58c , M. Li 15a , Q. Li 15d , Q.Y. Li 58a , S. Li 58d,58c , X. Li 58c , Y. Li 148 , Z. Liang 15a , B. Liberti 71a , A. Liblong 164 , K. Lie 61c , S. Liem 118 , A. Limosani 154 , C.Y. Lin 31 , K. Lin 104 , T.H. Lin 97 , R.A. Linck 63 , J.H. Lindon 21 , B.E. Lindquist 152 , A.L. Lionti 52 , E. Lipeles 134 , A. Lipniacka 17 , M. Lisovyi 59b , T.M. Liss 170,as , A. Lister 172 , A.M. Litke 143 , J.D. Little 8 , B. Liu 76 , B.L Liu 6 , H.B. Liu 26b , H. Liu 103 , J.B. Liu 58a , J.K.K. Liu 132 , K. Liu 133 , M. Liu 58a , The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 245 P. Liu 18 , Y. Liu 15a , Y.L. Liu 58a , Y.W. Liu 58a , M. Livan 68a,68b , A. Lleres 56 , J. Llorente Merino 15a , S.L. Lloyd 90 , C.Y. Lo 61b , F. Lo Sterzo 41 , E.M. Lobodzinska 44 , P. Loch 7 , T. Lohse 19 , K. Lohwasser 146 , M. Lokajicek 138 , J.D. Long 170 , R.E. Long 87 , L. Longo 65a,65b , K.A. Looper 123 , J.A. Lopez 144b , I. Lopez Paz 98 , A. Lopez Solis 146 , J. Lorenz 112 , N. Lorenzo Martinez 5 , M. Losada 22 , P.J. Lösel 112 , A. Lösle 50 , X. Lou 44 , X. Lou 15a , A. Lounis 129 , J. Love 6 , P.A. Love 87 , J.J. Lozano Bahilo 171 , H. Lu 61a , M. Lu 58a , Y.J. Lu 62 , H.J. Lubatti 145 , C. Luci 70a,70b , A. Lucotte 56 , C. Luedtke 50 , F. Luehring 63 , I. Luise 133 , L. Luminari 70a , B. Lund-Jensen 151 , M.S. Lutz 100 , P.M. Luzi 133 , D. Lynn 26b , R. Lysak 138 , E. Lytken 94 , F. Lyu 15a , V. Lyubushkin 77 , T. Lyubushkina 77 , H. Ma 26b , L.L. Ma 58b , Y. Ma 58b , G. Maccarrone 49 , A. Macchiolo 113 , C.M. Macdonald 146 , J. Machado Miguens 134,137b , D. Madaffari 171 , R. Madar 37 , W.F. Mader 46 , N. Madysa 46 , J. Maeda 80 , K. Maekawa 160 , S. Maeland 17 , T. Maeno 26b , M. Maerker 46 , A.S. Maevskiy 111 , V. Magerl 50 , D.J. Mahon 38 , C. Maidantchik 78b , T. Maier 112 , A. Maio 137a,137b,137d , O. Majersky 29a , S. Majewski 128 , Y. Makida 79 , N. Makovec 129 , B. Malaescu 133 , Pa. Malecki 82 , V.P. Maleev 135 , F. Malek 56 , U. Mallik 75 , D. Malon 6 , C. Malone 31 , S. Maltezos 10 , S. Malyukov 35 , J. Mamuzic 171 , G. Mancini 49 , I. Mandić 89 , J. Maneira 137a , L. Manhaes de Andrade Filho 78a , J. Manjarres Ramos 46 , K.H. Mankinen 94 , A. Mann 112 , A. Manousos 74 , B. Mansoulie 142 , S. Manzoni 66a,66b , A. Marantis 159 , G. Marceca 30 , L. March 52 , L. Marchese 132 , G. Marchiori 133 , M. Marcisovsky 138 , C. Marcon 94 , C.A. Marin Tobon 35 , M. Marjanovic 37 , F. Marroquim 78b , Z. Marshall 18 , M.U.F Martensson 169 , S. Marti-Garcia 171 , C.B. Martin 123 , T.A. Martin 175 , V.J. Martin 48 , B. Martin dit Latour 17 , M. Martinez 14,y , V.I. Martinez Outschoorn 100 , S. Martin-Haugh 141 , V.S. Martoiu 28b , A.C. Martyniuk 92 , A. Marzin 35 , L. Masetti 97 , T. Mashimo 160 , R. Mashinistov 108 , J. Masik 98 , A.L. Maslennikov 120b,120a , L.H. Mason 102 , L. Massa 71a,71b , P. Massarotti 67a,67b , P. Mastrandrea 152 , A. Mastroberardino 40b,40a , T. Masubuchi 160 , P. Mättig 24 , J. Maurer 28b , B. Maček 89 , S.J. Maxfield 88 , D.A. Maximov 120b,120a , R. Mazini 155 , I. Maznas 159 , S.M. Mazza 143 , S.P. Mc Kee 103 , A. McCarn Deiana 41 , T.G. McCarthy 113 , L.I. McClymont 92 , W.P. McCormack 18 , E.F. McDonald 102 , J.A. Mcfayden 35 , G. Mchedlidze 51 , M.A. McKay 41 , K.D. McLean 173 , S.J. McMahon 141 , P.C. McNamara 102 , C.J. McNicol 175 , R.A. McPherson 173,ac , J.E. Mdhluli 32c , Z.A. Meadows 100 , S. Meehan 145 , T.M. Megy 50 , S. Mehlhase 112 , A. Mehta 88 , T. Meideck 56 , B. Meirose 42 , D. Melini 171,aw , B.R. Mellado Garcia 32c , J.D. Mellenthin 51 , M. Melo 29a , F. Meloni 44 , A. Melzer 24 , S.B. Menary 98 , E.D. Mendes Gouveia 137a , L. Meng 88 , X.T. Meng 103 , S. Menke 113 , E. Meoni 40b,40a , S. Mergelmeyer 19 , S.A.M. Merkt 136 , C. Merlassino 20 , P. Mermod 52 , L. Merola 67a,67b , C. Meroni 66a , A. Messina 70a,70b , J. Metcalfe 6 , A.S. Mete 168 , C. Meyer 63 , J. Meyer 157 , J-P. Meyer 142 , H. Meyer Zu Theenhausen 59a , F. Miano 153 , R.P. Middleton 141 , L. Mijović 48 , G. Mikenberg 177 , M. Mikestikova 138 , M. Mikuž 89 , M. Milesi 102 , A. Milic 164 , D.A. Millar 90 , D.W. Miller 36 , A. Milov 177 , D.A. Milstead 43a,43b , R.A. Mina 150,q , A.A. Minaenko 121 , M. Miñano Moya 171 , I.A. Minashvili 156b , A.I. Mincer 122 , B. Mindur 81a , M. Mineev 77 , Y. Minegishi 160 , Y. Ming 178 , L.M. Mir 14 , A. Mirto 65a,65b , K.P. Mistry 134 , T. Mitani 176 , J. Mitrevski 112 , V.A. Mitsou 171 , M. Mittal 58c , A. Miucci 20 , P.S. Miyagawa 146 , A. Mizukami 79 , J.U. Mjörnmark 94 , T. Mkrtchyan 181 , M. Mlynarikova 140 , T. Moa 43a,43b , K. Mochizuki 107 , P. Mogg 50 , S. Mohapatra 38 , S. Molander 43a,43b , R. Moles-Valls 24 , M.C. Mondragon 104 , K. Mönig 44 , J. Monk 39 , E. Monnier 99 , A. Montalbano 149 , J. Montejo Berlingen 35 , F. Monticelli 86 , S. Monzani 66a , N. Morange 129 , D. Moreno 22 , M. Moreno Llácer 35 , P. Morettini 53b , M. Morgenstern 118 , S. Morgenstern 46 , D. Mori 149 , M. Morii 57 , M. Morinaga 176 , V. Morisbak 131 , A.K. Morley 35 , G. Mornacchi 35 , A.P. Morris 92 , J.D. Morris 90 , L. Morvaj 152 , P. Moschovakos 10 , M. Mosidze 156b , H.J. Moss 146 , J. Moss 150,n , K. Motohashi 162 , R. Mount 150 , E. Mountricha 35 , E.J.W. Moyse 100 , S. Muanza 99 , F. Mueller 113 , J. Mueller 136 , R.S.P. Mueller 112 , D. Muenstermann 87 , G.A. Mullier 94 , F.J. Munoz Sanchez 98 , P. Murin 29b , W.J. Murray 175,141 , A. Murrone 66a,66b , M. Muškinja 89 , C. Mwewa 32a , A.G. Myagkov 121,an , J. Myers 128 , M. Myska 139 , B.P. Nachman 18 , O. Nackenhorst 45 , K. Nagai 132 , K. Nagano 79 , Y. Nagasaka 60 , M. Nagel 50 , E. Nagy 99 , A.M. Nairz 35 , Y. Nakahama 115 , K. Nakamura 79 , T. Nakamura 160 , I. Nakano 124 , H. Nanjo 130 , F. Napolitano 59a , R.F. Naranjo Garcia 44 , R. Narayan 11 , D.I. Narrias Villar 59a , I. Naryshkin 135 , T. Naumann 44 , G. Navarro 22 , R. Nayyar 7 , H.A. Neal 103,∗ , P.Y. Nechaeva 108 , T.J. Neep 142 , A. Negri 68a,68b , M. Negrini 23b , S. Nektarijevic 117 , C. Nellist 51 , M.E. Nelson 132 , S. Nemecek 138 , P. Nemethy 122 , M. Nessi 35,f , M.S. Neubauer 170 , M. Neumann 179 , P.R. Newman 21 , T.Y. Ng 61c , Y.S. Ng 19 , Y.W.Y. 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Paredes Hernandez 61b , S.R. Paredes Saenz 132 , B. Parida 163 , T.H. Park 33 , A.J. Parker 87 , K.A. Parker 44 , M.A. Parker 31 , F. Parodi 53b,53a , J.A. Parsons 38 , U. Parzefall 50 , V.R. Pascuzzi 164 , J.M.P. Pasner 143 , E. Pasqualucci 70a , S. Passaggio 53b , F. Pastore 91 , P. Pasuwan 43a,43b , S. Pataraia 97 , J.R. Pater 98 , A. Pathak 178,k , T. Pauly 35 , B. Pearson 113 , M. Pedersen 131 , L. Pedraza Diaz 117 , R. Pedro 137a,137b , S.V. Peleganchuk 120b,120a , O. Penc 138 , C. Peng 15d , H. Peng 58a , B.S. Peralva 78a , M.M. Perego 129 , A.P. Pereira Peixoto 137a , D.V. Perepelitsa 26b , F. Peri 19 , L. Perini 66a,66b , H. Pernegger 35 , S. Perrella 67a,67b , V.D. Peshekhonov 77,∗ , K. Peters 44 , R.F.Y. Peters 98 , B.A. Petersen 35 , T.C. Petersen 39 , E. Petit 56 , A. Petridis 1 , C. Petridou 159 , P. Petroff 129 , M. Petrov 132 , F. Petrucci 72a,72b , M. Pettee 180 , N.E. Pettersson 100 , A. Peyaud 142 , R. Pezoa 144b , T. Pham 102 , F.H. Phillips 104 , P.W. 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Proudfoot 6 , M. Przybycien 81a , A. Puri 170 , P. Puzo 129 , J. Qian 103 , Y. Qin 98 , A. Quadt 51 , M. Queitsch-Maitland 44 , A. Qureshi 1 , P. Rados 102 , F. Ragusa 66a,66b , G. Rahal 95 , J.A. Raine 52 , S. Rajagopalan 26b , A. Ramirez Morales 90 , K. Ran 15a , T. Rashid 129 , S. Raspopov 5 , M.G. Ratti 66a,66b , D.M. Rauch 44 , F. Rauscher 112 , S. Rave 97 , B. Ravina 146 , I. Ravinovich 177 , J.H. Rawling 98 , M. Raymond 35 , A.L. Read 131 , N.P. Readioff 56 , M. Reale 65a,65b , D.M. Rebuzzi 68a,68b , A. Redelbach 174 , G. Redlinger 26b , R. Reece 143 , R.G. Reed 32c , K. Reeves 42 , L. Rehnisch 19 , J. Reichert 134 , D. Reikher 158 , A. Reiss 97 , A. Rej 148 , C. Rembser 35 , H. Ren 15d , M. Rescigno 70a , S. Resconi 66a , E.D. Resseguie 134 , S. Rettie 172 , E. Reynolds 21 , O.L. Rezanova 120b,120a , P. Reznicek 140 , E. Ricci 73a,73b , R. Richter 113 , S. Richter 44 , E. Richter-Was 81b , O. Ricken 24 , M. Ridel 133 , P. Rieck 113 , C.J. Riegel 179 , O. Rifki 44 , M. Rijssenbeek 152 , A. Rimoldi 68a,68b , M. Rimoldi 20 , L. Rinaldi 23b , G. Ripellino 151 , B. Ristić 87 , E. Ritsch 35 , I. Riu 14 , J.C. Rivera Vergara 144a , F. Rizatdinova 126 , E. Rizvi 90 , C. Rizzi 14 , R.T. Roberts 98 , S.H. Robertson 101,ac , D. Robinson 31 , J.E.M. Robinson 44 , A. Robson 55 , E. Rocco 97 , C. Roda 69a,69b , Y. Rodina 99 , S. Rodriguez Bosca 171 , A. Rodriguez Perez 14 , D. Rodriguez Rodriguez 171 , A.M. Rodríguez Vera 165b , S. Roe 35 , C.S. Rogan 57 , O. Røhne 131 , R. Röhrig 113 , C.P.A. Roland 63 , J. Roloff 57 , A. Romaniouk 110 , M. Romano 23b,23a , N. Rompotis 88 , M. Ronzani 122 , L. Roos 133 , S. Rosati 70a , K. Rosbach 50 , N-A. Rosien 51 , B.J. Rosser 134 , E. Rossi 44 , E. Rossi 72a,72b , E. Rossi 67a,67b , L.P. Rossi 53b , L. Rossini 66a,66b , J.H.N. Rosten 31 , R. Rosten 14 , M. Rotaru 28b , J. Rothberg 145 , D. Rousseau 129 , D. Roy 32c , A. Rozanov 99 , Y. Rozen 157 , X. Ruan 32c , F. Rubbo 150 , F. Rühr 50 , A. Ruiz-Martinez 171 , Z. Rurikova 50 , N.A. Rusakovich 77 , H.L. Russell 101 , J.P. Rutherfoord 7 , E.M. Rüttinger 44,l , Y.F. Ryabov 135 , M. Rybar 38 , G. Rybkin 129 , S. Ryu 6 , A. Ryzhov 121 , G.F. Rzehorz 51 , The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 247 P. Sabatini 51 , G. Sabato 118 , S. Sacerdoti 129 , H.F-W. Sadrozinski 143 , R. Sadykov 77 , F. Safai Tehrani 70a , P. Saha 119 , M. Sahinsoy 59a , A. Sahu 179 , M. Saimpert 44 , M. Saito 160 , T. Saito 160 , H. Sakamoto 160 , A. Sakharov 122,am , D. Salamani 52 , G. Salamanna 72a,72b , J.E. Salazar Loyola 144b , P.H. Sales De Bruin 169 , D. Salihagic 113,∗ , A. Salnikov 150 , J. Salt 171 , D. Salvatore 40b,40a , F. Salvatore 153 , A. Salvucci 61a,61b,61c , A. Salzburger 35 , J. Samarati 35 , D. Sammel 50 , D. Sampsonidis 159 , D. Sampsonidou 159 , J. Sánchez 171 , A. Sanchez Pineda 64a,64c , H. Sandaker 131 , C.O. Sander 44 , M. Sandhoff 179 , C. Sandoval 22 , D.P.C. Sankey 141 , M. Sannino 53b,53a , Y. Sano 115 , A. Sansoni 49 , C. Santoni 37 , H. Santos 137a , I. Santoyo Castillo 153 , A. Santra 171 , A. Sapronov 77 , J.G. Saraiva 137a,137d , O. Sasaki 79 , K. Sato 166 , E. Sauvan 5 , P. Savard 164,av , N. Savic 113 , R. Sawada 160 , C. Sawyer 141 , L. Sawyer 93,ak , C. Sbarra 23b , A. Sbrizzi 23a , T. Scanlon 92 , J. Schaarschmidt 145 , P. Schacht 113 , B.M. Schachtner 112 , D. Schaefer 36 , L. Schaefer 134 , J. Schaeffer 97 , S. Schaepe 35 , U. Schäfer 97 , A.C. Schaffer 129 , D. Schaile 112 , R.D. Schamberger 152 , N. Scharmberg 98 , V.A. Schegelsky 135 , D. Scheirich 140 , F. Schenck 19 , M. Schernau 168 , C. Schiavi 53b,53a , S. Schier 143 , L.K. Schildgen 24 , Z.M. Schillaci 27 , E.J. Schioppa 35 , M. Schioppa 40b,40a , K.E. Schleicher 50 , S. Schlenker 35 , K.R. Schmidt-Sommerfeld 113 , K. Schmieden 35 , C. Schmitt 97 , S. Schmitt 44 , S. Schmitz 97 , J.C. Schmoeckel 44 , U. Schnoor 50 , L. Schoeffel 142 , A. Schoening 59b , E. Schopf 132 , M. Schott 97 , J.F.P. Schouwenberg 117 , J. Schovancova 35 , S. Schramm 52 , A. Schulte 97 , H-C. Schultz-Coulon 59a , M. Schumacher 50 , B.A. Schumm 143 , Ph. Schune 142 , A. Schwartzman 150 , T.A. Schwarz 103 , Ph. Schwemling 142 , R. Schwienhorst 104 , A. Sciandra 24 , G. Sciolla 27 , M. Scornajenghi 40b,40a , F. Scuri 69a , F. Scutti 102 , L.M. Scyboz 113 , C.D. Sebastiani 70a,70b , P. Seema 19 , S.C. Seidel 116 , A. Seiden 143 , T. Seiss 36 , J.M. Seixas 78b , G. Sekhniaidze 67a , K. Sekhon 103 , S.J. Sekula 41 , N. Semprini-Cesari 23b,23a , S. Sen 47 , S. Senkin 37 , C. Serfon 131 , L. Serin 129 , L. Serkin 64a,64b , M. Sessa 58a , H. Severini 125 , F. Sforza 167 , A. Sfyrla 52 , E. Shabalina 51 , J.D. Shahinian 143 , N.W. Shaikh 43a,43b , D. Shaked Renous 177 , L.Y. Shan 15a , R. Shang 170 , J.T. Shank 25 , M. Shapiro 18 , A.S. Sharma 1 , A. Sharma 132 , P.B. Shatalov 109 , K. Shaw 153 , S.M. Shaw 98 , A. Shcherbakova 135 , Y. Shen 125 , N. Sherafati 33 , A.D. Sherman 25 , P. Sherwood 92 , L. Shi 155,ar , S. Shimizu 79 , C.O. Shimmin 180 , Y. Shimogama 176 , M. Shimojima 114 , I.P.J. Shipsey 132 , S. Shirabe 85 , M. Shiyakova 77 , J. Shlomi 177 , A. Shmeleva 108 , D. Shoaleh Saadi 107 , M.J. Shochet 36 , S. Shojaii 102 , D.R. Shope 125 , S. Shrestha 123 , E. Shulga 110 , P. Sicho 138 , A.M. Sickles 170 , P.E. Sidebo 151 , E. Sideras Haddad 32c , O. Sidiropoulou 35 , A. Sidoti 23b,23a , F. Siegert 46 , Dj. Sijacki 16 , J. Silva 137a , M. Silva Jr. 178 , M.V. Silva Oliveira 78a , S.B. Silverstein 43a , S. Simion 129 , E. Simioni 97 , M. Simon 97 , R. Simoniello 97 , P. Sinervo 164 , N.B. Sinev 128 , M. Sioli 23b,23a , I. Siral 103 , S.Yu. Sivoklokov 111 , J. Sjölin 43a,43b , P. Skubic 125 , M. Slater 21 , T. Slavicek 139 , M. Slawinska 82 , K. Sliwa 167 , R. Slovak 140 , V. Smakhtin 177 , B.H. Smart 5 , J. Smiesko 29a , N. Smirnov 110 , S.Yu. Smirnov 110 , Y. Smirnov 110 , L.N. Smirnova 111 , O. Smirnova 94 , J.W. Smith 51 , M. Smizanska 87 , K. Smolek 139 , A. Smykiewicz 82 , A.A. Snesarev 108 , I.M. Snyder 128 , S. Snyder 26b , R. Sobie 173,ac , A.M. Soffa 168 , A. Soffer 158 , A. Søgaard 48 , F. Sohns 51 , G. Sokhrannyi 89 , C.A. Solans Sanchez 35 , M. Solar 139 , E.Yu. Soldatov 110 , U. Soldevila 171 , A.A. Solodkov 121 , A. Soloshenko 77 , O.V. Solovyanov 121 , V. Solovyev 135 , P. Sommer 146 , H. Son 167 , W. Song 141 , W.Y. Song 165b , A. Sopczak 139 , F. Sopkova 29b , C.L. Sotiropoulou 69a,69b , S. Sottocornola 68a,68b , R. Soualah 64a,64c,i , A.M. Soukharev 120b,120a , D. South 44 , S. Spagnolo 65a,65b , M. Spalla 113 , M. Spangenberg 175 , F. Spanò 91 , D. Sperlich 19 , T.M. Spieker 59a , R. Spighi 23b , G. Spigo 35 , L.A. Spiller 102 , D.P. Spiteri 55 , M. Spousta 140 , A. Stabile 66a,66b , R. Stamen 59a , S. Stamm 19 , E. Stanecka 82 , R.W. Stanek 6 , C. Stanescu 72a , B. Stanislaus 132 , M.M. Stanitzki 44 , B. Stapf 118 , E.A. Starchenko 121 , G.H. Stark 143 , J. Stark 56 , S.H Stark 39 , P. Staroba 138 , P. Starovoitov 59a , S. Stärz 101 , R. 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Takasugi 113 , K. Takeda 80 , T. Takeshita 147 , Y. Takubo 79 , M. Talby 99 , A.A. Talyshev 120b,120a , J. Tanaka 160 , M. Tanaka 162 , R. Tanaka 129 , B.B. Tannenwald 123 , 248 The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 S. Tapia Araya 170 , S. Tapprogge 97 , A. Tarek Abouelfadl Mohamed 133 , S. Tarem 157 , G. Tarna 28b,e , G.F. Tartarelli 66a , P. Tas 140 , M. Tasevsky 138 , T. Tashiro 83 , E. Tassi 40b,40a , A. Tavares Delgado 137a,137b , Y. Tayalati 34e , A.J. Taylor 48 , G.N. Taylor 102 , P.T.E. Taylor 102 , W. Taylor 165b , A.S. Tee 87 , R. Teixeira De Lima 150 , P. Teixeira-Dias 91 , H. Ten Kate 35 , J.J. Teoh 118 , S. Terada 79 , K. Terashi 160 , J. Terron 96 , S. Terzo 14 , M. Testa 49 , R.J. Teuscher 164,ac , S.J. Thais 180 , T. Theveneaux-Pelzer 44 , F. Thiele 39 , D.W. Thomas 91 , J.P. Thomas 21 , A.S. Thompson 55 , P.D. Thompson 21 , L.A. Thomsen 180 , E. Thomson 134 , Y. Tian 38 , R.E. Ticse Torres 51 , V.O. Tikhomirov 108,ao , Yu.A. Tikhonov 120b,120a , S. Timoshenko 110 , P. Tipton 180 , S. Tisserant 99 , K. Todome 162 , S. Todorova-Nova 5 , S. Todt 46 , J. Tojo 85 , S. Tokár 29a , K. Tokushuku 79 , E. Tolley 123 , K.G. Tomiwa 32c , M. Tomoto 115 , L. Tompkins 150,q , K. Toms 116 , B. Tong 57 , P. Tornambe 50 , E. Torrence 128 , H. Torres 46 , E. Torró Pastor 145 , C. Tosciri 132 , J. Toth 99,ab , F. Touchard 99 , D.R. Tovey 146 , C.J. Treado 122 , T. Trefzger 174 , F. Tresoldi 153 , A. Tricoli 26b , I.M. Trigger 165a , S. Trincaz-Duvoid 133 , W. Trischuk 164 , B. Trocmé 56 , A. Trofymov 129 , C. Troncon 66a , M. Trovatelli 173 , F. Trovato 153 , L. Truong 32b , M. Trzebinski 82 , A. Trzupek 82 , F. Tsai 44 , J.C-L. Tseng 132 , P.V. Tsiareshka 105,ai , A. Tsirigotis 159 , N. Tsirintanis 9 , V. Tsiskaridze 152 , E.G. Tskhadadze 156a , I.I. Tsukerman 109 , V. Tsulaia 18 , S. Tsuno 79 , D. Tsybychev 152,163 , Y. Tu 61b , A. Tudorache 28b , V. Tudorache 28b , T.T. Tulbure 28a , A.N. Tuna 57 , S. Turchikhin 77 , D. Turgeman 177 , I. Turk Cakir 4b,t , R.J. Turner 21 , R.T. Turra 66a , P.M. Tuts 38 , S Tzamarias 159 , E. Tzovara 97 , G. Ucchielli 45 , I. Ueda 79 , M. Ughetto 43a,43b , F. Ukegawa 166 , G. Unal 35 , A. Undrus 26b , G. Unel 168 , F.C. Ungaro 102 , Y. Unno 79 , K. Uno 160 , J. Urban 29b , P. Urquijo 102 , G. Usai 8 , J. Usui 79 , L. Vacavant 99 , V. Vacek 139 , B. Vachon 101 , K.O.H. Vadla 131 , A. Vaidya 92 , C. Valderanis 112 , E. Valdes Santurio 43a,43b , M. Valente 52 , S. Valentinetti 23b,23a , A. Valero 171 , L. Valéry 44 , R.A. Vallance 21 , A. Vallier 5 , J.A. Valls Ferrer 171 , T.R. Van Daalen 14 , H. Van der Graaf 118 , P. Van Gemmeren 6 , I. Van Vulpen 118 , M. Vanadia 71a,71b , W. Vandelli 35 , A. Vaniachine 163 , P. Vankov 118 , R. Vari 70a , E.W. Varnes 7 , C. Varni 53b,53a , T. Varol 41 , D. Varouchas 129 , K.E. Varvell 154 , G.A. Vasquez 144b , J.G. Vasquez 180 , F. Vazeille 37 , D. Vazquez Furelos 14 , T. Vazquez Schroeder 35 , J. Veatch 51 , V. Vecchio 72a,72b , L.M. 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Wahrmund 46 , K. Wakamiya 80 , V.M. Walbrecht 113 , J. Walder 87 , R. Walker 112 , S.D. Walker 91 , W. Walkowiak 148 , V. Wallangen 43a,43b , A.M. Wang 57 , C. Wang 58b , F. Wang 178 , H. Wang 18 , H. Wang 3 , J. Wang 154 , J. Wang 59b , P. Wang 41 , Q. Wang 125 , R.-J. Wang 133 , R. Wang 58a , R. Wang 6 , S.M. Wang 155 , W.T. Wang 58a , W. Wang 15c,ad , W.X. Wang 58a,ad , Y. Wang 58a,al , Z. Wang 58c , C. Wanotayaroj 44 , A. Warburton 101 , C.P. Ward 31 , D.R. Wardrope 92 , A. Washbrook 48 , P.M. Watkins 21 , A.T. Watson 21 , M.F. Watson 21 , G. Watts 145 , S. Watts 98 , B.M. Waugh 92 , A.F. Webb 11 , S. Webb 97 , C. Weber 180 , M.S. Weber 20 , S.A. Weber 33 , S.M. Weber 59a , A.R. Weidberg 132 , J. Weingarten 45 , M. Weirich 97 , C. Weiser 50 , P.S. Wells 35 , T. Wenaus 26b , T. Wengler 35 , S. Wenig 35 , N. Wermes 24 , M.D. Werner 76 , P. Werner 35 , M. Wessels 59a , T.D. Weston 20 , K. Whalen 128 , N.L. Whallon 145 , A.M. Wharton 87 , A.S. White 103 , A. White 8 , M.J. White 1 , R. White 144b , D. Whiteson 168 , B.W. Whitmore 87 , F.J. Wickens 141 , W. Wiedenmann 178 , M. Wielers 141 , C. Wiglesworth 39 , L.A.M. Wiik-Fuchs 50 , F. Wilk 98 , H.G. Wilkens 35 , L.J. Wilkins 91 , H.H. Williams 134 , S. Williams 31 , C. Willis 104 , S. Willocq 100 , J.A. Wilson 21 , I. Wingerter-Seez 5 , E. Winkels 153 , F. Winklmeier 128 , O.J. Winston 153 , B.T. Winter 50 , M. Wittgen 150 , M. Wobisch 93 , A. Wolf 97 , T.M.H. Wolf 118 , R. Wolff 99 , J. Wollrath 50 , M.W. Wolter 82 , H. Wolters 137a,137c , V.W.S. Wong 172 , N.L. Woods 143 , S.D. Worm 21 , B.K. Wosiek 82 , K.W. Woźniak 82 , K. Wraight 55 , M. Wu 36 , S.L. Wu 178 , X. Wu 52 , Y. Wu 58a , T.R. Wyatt 98 , B.M. Wynne 48 , S. Xella 39 , Z. Xi 103 , L. Xia 175 , D. Xu 15a , H. Xu 58a,e , L. Xu 26b , T. Xu 142 , W. Xu 103 , Z. Xu 150 , B. Yabsley 154 , S. Yacoob 32a , K. Yajima 130 , D.P. Yallup 92 , D. Yamaguchi 162 , Y. Yamaguchi 162 , A. Yamamoto 79 , T. Yamanaka 160 , F. Yamane 80 , M. Yamatani 160 , T. Yamazaki 160 , Y. Yamazaki 80 , Z. Yan 25 , H.J. Yang 58c,58d , H.T. Yang 18 , S. Yang 75 , The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 249 Y. Yang 160 , Z. Yang 17 , W-M. Yao 18 , Y.C. Yap 44 , Y. Yasu 79 , E. Yatsenko 58c,58d , J. Ye 41 , S. Ye 26b , I. Yeletskikh 77 , E. Yigitbasi 25 , E. Yildirim 97 , K. Yorita 176 , K. Yoshihara 134 , C.J.S. Young 35 , C. Young 150 , J. Yu 8 , J. Yu 76 , X. Yue 59a , S.P.Y. Yuen 24 , B. Zabinski 82 , G. Zacharis 10 , E. Zaffaroni 52 , R. Zaidan 14 , A.M. Zaitsev 121,an , T. Zakareishvili 156b , N. Zakharchuk 33 , S. Zambito 57 , D. Zanzi 35 , D.R. Zaripovas 55 , S.V. Zeißner 45 , C. Zeitnitz 179 , G. Zemaityte 132 , J.C. Zeng 170 , Q. Zeng 150 , O. Zenin 121 , D. Zerwas 129 , M. Zgubič 132 , D.F. Zhang 58b , D. Zhang 103 , F. Zhang 178 , G. Zhang 58a , G. Zhang 15b , H. Zhang 15c , J. Zhang 6 , L. Zhang 15c , L. Zhang 58a , M. Zhang 170 , P. Zhang 15c , R. Zhang 58a , R. Zhang 24 , X. Zhang 58b , Y. Zhang 15d , Z. Zhang 129 , P. Zhao 47 , Y. Zhao 58b,129,aj , Z. Zhao 58a , A. Zhemchugov 77 , Z. Zheng 103 , D. Zhong 170 , B. Zhou 103 , C. Zhou 178 , M.S. Zhou 15d , M. Zhou 152 , N. Zhou 58c , Y. Zhou 7 , C.G. Zhu 58b , H.L. Zhu 58a , H. Zhu 15a , J. Zhu 103 , Y. Zhu 58a , X. Zhuang 15a , K. Zhukov 108 , V. Zhulanov 120b,120a , A. Zibell 174 , D. Zieminska 63 , N.I. Zimine 77 , S. Zimmermann 50 , Z. Zinonos 113 , M. Ziolkowski 148 , G. Zobernig 178 , A. Zoccoli 23b,23a , K. Zoch 51 , T.G. Zorbas 146 , R. Zou 36 , M. Zur Nedden 19 , L. Zwalinski 35 1 Department of Physics, University of Adelaide, Adelaide, Australia 2 Physics Department, SUNY Albany, Albany, NY, United States of America 3 Department of Physics, University of Alberta, Edmonton, AB, Canada 4 (a) Department of Physics, Ankara University, Ankara; (b) Istanbul Aydin University, Istanbul; (c) Division of Physics, TOBB University of Economics and Technology, Ankara, Turkey 5 LAPP, Université Grenoble Alpes, Université Savoie Mont Blanc, CNRS/IN2P3, Annecy, France 6 High Energy Physics Division, Argonne National Laboratory, Argonne, IL, United States of America 7 Department of Physics, University of Arizona, Tucson, AZ, United States of America 8 Department of Physics, University of Texas at Arlington, Arlington, TX, United States of America 9 Physics Department, National and Kapodistrian University of Athens, Athens, Greece 10 Physics Department, National Technical University of Athens, Zografou, Greece 11 Department of Physics, University of Texas at Austin, Austin, TX, United States of America 12 (a) Bahcesehir University, Faculty of Engineering and Natural Sciences, Istanbul; (b) Istanbul Bilgi University, Faculty of Engineering and Natural Sciences, Istanbul; (c) Department of Physics, Bogazici University, Istanbul; (d) Department of Physics Engineering, Gaziantep University, Gaziantep, Turkey 13 Institute of Physics, Azerbaijan Academy of Sciences, Baku, Azerbaijan 14 Institut de Física d’Altes Energies (IFAE), Barcelona Institute of Science and Technology, Barcelona, Spain 15 (a) Institute of High Energy Physics, Chinese Academy of Sciences, Beijing; (b) Physics Department, Tsinghua University, Beijing; (c) Department of Physics, Nanjing University, Nanjing; (d) University of Chinese Academy of Science (UCAS), Beijing, China 16 Institute of Physics, University of Belgrade, Belgrade, Serbia 17 Department for Physics and Technology, University of Bergen, Bergen, Norway 18 Physics Division, Lawrence Berkeley National Laboratory and University of California, Berkeley, CA, United States of America 19 Institut für Physik, Humboldt Universität zu Berlin, Berlin, Germany 20 Albert Einstein Center for Fundamental Physics and Laboratory for High Energy Physics, University of Bern, Bern, Switzerland 21 School of Physics and Astronomy, University of Birmingham, Birmingham, United Kingdom 22 Centro de Investigaciónes, Universidad Antonio Nariño, Bogota, Colombia 23 (a) INFN Bologna and Universita’ di Bologna, Dipartimento di Fisica; (b) INFN Sezione di Bologna, Italy 24 Physikalisches Institut, Universität Bonn, Bonn, Germany 25 Department of Physics, Boston University, Boston, MA, United States of America 26 (a) University of Colorado Boulder, Department of Physics, CO; (b) Physics Department, Brookhaven National Laboratory, Upton, NY, United States of America 27 Department of Physics, Brandeis University, Waltham, MA, United States of America 28 (a) Transilvania University of Brasov, Brasov; (b) Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest; (c) Department of Physics, Alexandru Ioan Cuza University of Iasi, Iasi; (d) National Institute for Research and Development of Isotopic and Molecular Technologies, Physics Department, Cluj-Napoca; (e) University Politehnica Bucharest, Bucharest; (f ) West University in Timisoara, Timisoara, Romania 29 (a) Faculty of Mathematics, Physics and Informatics, Comenius University, Bratislava; (b) Department of Subnuclear Physics, Institute of Experimental Physics of the Slovak Academy of Sciences, Kosice, Slovak Republic 30 Departamento de Física, Universidad de Buenos Aires, Buenos Aires, Argentina 31 Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom 32 (a) Department of Physics, University of Cape Town, Cape Town; (b) Department of Mechanical Engineering Science, University of Johannesburg, Johannesburg; (c) School of Physics, University of the Witwatersrand, Johannesburg, South Africa 33 Department of Physics, Carleton University, Ottawa, ON, Canada 34 (a) Faculté des Sciences Ain Chock, Réseau Universitaire de Physique des Hautes Energies – Université Hassan II, Casablanca; (b) Centre National de l’Energie des Sciences Techniques Nucleaires (CNESTEN), Rabat; (c) Faculté des Sciences Semlalia, Université Cadi Ayyad, LPHEA, Marrakech; (d) Faculté des Sciences, Université Mohamed Premier and LPTPM, Oujda; (e) Faculté des sciences, Université Mohammed V, Rabat, Morocco 35 CERN, Geneva, Switzerland 36 Enrico Fermi Institute, University of Chicago, Chicago, IL, United States of America 37 LPC, Université Clermont Auvergne, CNRS/IN2P3, Clermont-Ferrand, France 38 Nevis Laboratory, Columbia University, Irvington, NY, United States of America 39 Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark 40 (a) Dipartimento di Fisica, Università della Calabria, Rende; (b) INFN Gruppo Collegato di Cosenza, Laboratori Nazionali di Frascati, Italy 41 Physics Department, Southern Methodist University, Dallas, TX, United States of America 42 Physics Department, University of Texas at Dallas, Richardson, TX, United States of America 43 (a) Department of Physics, Stockholm University; (b) Oskar Klein Centre, Stockholm, Sweden 44 Deutsches Elektronen-Synchrotron DESY, Hamburg and Zeuthen, Germany 45 Lehrstuhl für Experimentelle Physik IV, Technische Universität Dortmund, Dortmund, Germany 46 Institut für Kern- und Teilchenphysik, Technische Universität Dresden, Dresden, Germany 47 Department of Physics, Duke University, Durham, NC, United States of America 48 SUPA – School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom 49 INFN e Laboratori Nazionali di Frascati, Frascati, Italy 50 Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany 51 II. Physikalisches Institut, Georg-August-Universität Göttingen, Göttingen, Germany 52 Département de Physique Nucléaire et Corpusculaire, Université de Genève, Genève, Switzerland 250 The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 53 (a) Dipartimento di Fisica, Università di Genova, Genova; (b) INFN Sezione di Genova, Italy 54 II. Physikalisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany 55 SUPA – School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom 56 LPSC, Université Grenoble Alpes, CNRS/IN2P3, Grenoble INP, Grenoble, France 57 Laboratory for Particle Physics and Cosmology, Harvard University, Cambridge, MA, United States of America 58 (a) Department of Modern Physics and State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China, Hefei; (b) Institute of Frontier and Interdisciplinary Science and Key Laboratory of Particle Physics and Particle Irradiation (MOE), Shandong University, Qingdao; (c) School of Physics and Astronomy, Shanghai Jiao Tong University, KLPPAC-MoE, SKLPPC, Shanghai; (d) Tsung-Dao Lee Institute, Shanghai, China 59 (a) Kirchhoff-Institut für Physik, Ruprecht-Karls-Universität Heidelberg, Heidelberg; (b) Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany 60 Faculty of Applied Information Science, Hiroshima Institute of Technology, Hiroshima, Japan 61 (a) Department of Physics, Chinese University of Hong Kong, Shatin, N.T., Hong Kong; (b) Department of Physics, University of Hong Kong, Hong Kong; (c) Department of Physics and Institute for Advanced Study, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China 62 Department of Physics, National Tsing Hua University, Hsinchu, Taiwan 63 Department of Physics, Indiana University, Bloomington, IN, United States of America 64 (a) INFN Gruppo Collegato di Udine, Sezione di Trieste, Udine; (b) ICTP, Trieste; (c) Dipartimento Politecnico di Ingegneria e Architettura, Università di Udine, Udine, Italy 65 (a) INFN Sezione di Lecce; (b) Dipartimento di Matematica e Fisica, Università del Salento, Lecce, Italy 66 (a) INFN Sezione di Milano; (b) Dipartimento di Fisica, Università di Milano, Milano, Italy 67 (a) INFN Sezione di Napoli; (b) Dipartimento di Fisica, Università di Napoli, Napoli, Italy 68 (a) INFN Sezione di Pavia; (b) Dipartimento di Fisica, Università di Pavia, Pavia, Italy 69 (a) INFN Sezione di Pisa; (b) Dipartimento di Fisica E. Fermi, Università di Pisa, Pisa, Italy 70 (a) INFN Sezione di Roma; (b) Dipartimento di Fisica, Sapienza Università di Roma, Roma, Italy 71 (a) INFN Sezione di Roma Tor Vergata; (b) Dipartimento di Fisica, Università di Roma Tor Vergata, Roma, Italy 72 (a) INFN Sezione di Roma Tre; (b) Dipartimento di Matematica e Fisica, Università Roma Tre, Roma, Italy 73 (a) INFN-TIFPA; (b) Università degli Studi di Trento, Trento, Italy 74 Institut für Astro- und Teilchenphysik, Leopold-Franzens-Universität, Innsbruck, Austria 75 University of Iowa, Iowa City, IA, United States of America 76 Department of Physics and Astronomy, Iowa State University, Ames, IA, United States of America 77 Joint Institute for Nuclear Research, Dubna, Russia 78 (a) Departamento de Engenharia Elétrica, Universidade Federal de Juiz de Fora (UFJF), Juiz de Fora; (b) Universidade Federal do Rio De Janeiro COPPE/EE/IF, Rio de Janeiro; (c) Universidade Federal de São João del Rei (UFSJ), São João del Rei; (d) Instituto de Física, Universidade de São Paulo, São Paulo, Brazil 79 KEK, High Energy Accelerator Research Organization, Tsukuba, Japan 80 Graduate School of Science, Kobe University, Kobe, Japan 81 (a) AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Krakow; (b) Marian Smoluchowski Institute of Physics, Jagiellonian University, Krakow, Poland 82 Institute of Nuclear Physics Polish Academy of Sciences, Krakow, Poland 83 Faculty of Science, Kyoto University, Kyoto, Japan 84 Kyoto University of Education, Kyoto, Japan 85 Research Center for Advanced Particle Physics and Department of Physics, Kyushu University, Fukuoka , Japan 86 Instituto de Física La Plata, Universidad Nacional de La Plata and CONICET, La Plata, Argentina 87 Physics Department, Lancaster University, Lancaster, United Kingdom 88 Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom 89 Department of Experimental Particle Physics, Jožef Stefan Institute and Department of Physics, University of Ljubljana, Ljubljana, Slovenia 90 School of Physics and Astronomy, Queen Mary University of London, London, United Kingdom 91 Department of Physics, Royal Holloway University of London, Egham, United Kingdom 92 Department of Physics and Astronomy, University College London, London, United Kingdom 93 Louisiana Tech University, Ruston, LA, United States of America 94 Fysiska institutionen, Lunds universitet, Lund, Sweden 95 Centre de Calcul de l’Institut National de Physique Nucléaire et de Physique des Particules (IN2P3), Villeurbanne, France 96 Departamento de Física Teorica C-15 and CIAFF, Universidad Autónoma de Madrid, Madrid, Spain 97 Institut für Physik, Universität Mainz, Mainz, Germany 98 School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom 99 CPPM, Aix-Marseille Université, CNRS/IN2P3, Marseille, France 100 Department of Physics, University of Massachusetts, Amherst, MA, United States of America 101 Department of Physics, McGill University, Montreal, QC, Canada 102 School of Physics, University of Melbourne, Victoria, Australia 103 Department of Physics, University of Michigan, Ann Arbor, MI, United States of America 104 Department of Physics and Astronomy, Michigan State University, East Lansing, MI, United States of America 105 B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk, Belarus 106 Research Institute for Nuclear Problems of Byelorussian State University, Minsk, Belarus 107 Group of Particle Physics, University of Montreal, Montreal, QC, Canada 108 P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow, Russia 109 Institute for Theoretical and Experimental Physics of the National Research Centre Kurchatov Institute, Moscow, Russia 110 National Research Nuclear University MEPhI, Moscow, Russia 111 D.V. Skobeltsyn Institute of Nuclear Physics, M.V. Lomonosov Moscow State University, Moscow, Russia 112 Fakultät für Physik, Ludwig-Maximilians-Universität München, München, Germany 113 Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), München, Germany 114 Nagasaki Institute of Applied Science, Nagasaki, Japan 115 Graduate School of Science and Kobayashi–Maskawa Institute, Nagoya University, Nagoya, Japan 116 Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM, United States of America 117 Institute for Mathematics, Astrophysics and Particle Physics, Radboud University Nijmegen/Nikhef, Nijmegen, Netherlands 118 Nikhef National Institute for Subatomic Physics and University of Amsterdam, Amsterdam, Netherlands 119 Department of Physics, Northern Illinois University, DeKalb, IL, United States of America 120 (a) Budker Institute of Nuclear Physics and NSU, SB RAS, Novosibirsk; (b) Novosibirsk State University Novosibirsk, Russia 121 Institute for High Energy Physics of the National Research Centre Kurchatov Institute, Protvino, Russia 122 Department of Physics, New York University, New York, NY, United States of America 123 Ohio State University, Columbus, OH, United States of America 124 Faculty of Science, Okayama University, Okayama, Japan 125 Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK, United States of America 126 Department of Physics, Oklahoma State University, Stillwater, OK, United States of America The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 251 127 Palacký University, RCPTM, Joint Laboratory of Optics, Olomouc, Czech Republic 128 Center for High Energy Physics, University of Oregon, Eugene, OR, United States of America 129 LAL, Université Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, Orsay, France 130 Graduate School of Science, Osaka University, Osaka, Japan 131 Department of Physics, University of Oslo, Oslo, Norway 132 Department of Physics, Oxford University, Oxford, United Kingdom 133 LPNHE, Sorbonne Université, Paris Diderot Sorbonne Paris Cité, CNRS/IN2P3, Paris, France 134 Department of Physics, University of Pennsylvania, Philadelphia, PA, United States of America 135 Konstantinov Nuclear Physics Institute of National Research Centre “Kurchatov Institute”, PNPI, St. Petersburg, Russia 136 Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, United States of America 137 (a) Laboratório de Instrumentação e Física Experimental de Partículas – LIP; (b) Departamento de Física, Faculdade de Ciências, Universidade de Lisboa, Lisboa; (c) Departamento de Física, Universidade de Coimbra, Coimbra; (d) Centro de Física Nuclear da Universidade de Lisboa, Lisboa; (e) Departamento de Física, Universidade do Minho, Braga; (f ) Universidad de Granada, Granada (Spain); (g) Dep. Física and CEFITEC of Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal 138 Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic 139 Czech Technical University in Prague, Prague, Czech Republic 140 Charles University, Faculty of Mathematics and Physics, Prague, Czech Republic 141 Particle Physics Department, Rutherford Appleton Laboratory, Didcot, United Kingdom 142 IRFU, CEA, Université Paris-Saclay, Gif-sur-Yvette, France 143 Santa Cruz Institute for Particle Physics, University of California Santa Cruz, Santa Cruz, CA, United States of America 144 (a) Departamento de Física, Pontificia Universidad Católica de Chile, Santiago; (b) Departamento de Física, Universidad Técnica Federico Santa María, Valparaíso, Chile 145 Department of Physics, University of Washington, Seattle, WA, United States of America 146 Department of Physics and Astronomy, University of Sheffield, Sheffield, United Kingdom 147 Department of Physics, Shinshu University, Nagano, Japan 148 Department Physik, Universität Siegen, Siegen, Germany 149 Department of Physics, Simon Fraser University, Burnaby, BC, Canada 150 SLAC National Accelerator Laboratory, Stanford, CA, United States of America 151 Physics Department, Royal Institute of Technology, Stockholm, Sweden 152 Departments of Physics and Astronomy, Stony Brook University, Stony Brook, NY, United States of America 153 Department of Physics and Astronomy, University of Sussex, Brighton, United Kingdom 154 School of Physics, University of Sydney, Sydney, Australia 155 Institute of Physics, Academia Sinica, Taipei, Taiwan 156 (a) E. Andronikashvili Institute of Physics, Iv. Javakhishvili Tbilisi State University, Tbilisi; (b) High Energy Physics Institute, Tbilisi State University, Tbilisi, Georgia 157 Department of Physics, Technion, Israel Institute of Technology, Haifa, Israel 158 Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv, Israel 159 Department of Physics, Aristotle University of Thessaloniki, Thessaloniki, Greece 160 International Center for Elementary Particle Physics and Department of Physics, University of Tokyo, Tokyo, Japan 161 Graduate School of Science and Technology, Tokyo Metropolitan University, Tokyo, Japan 162 Department of Physics, Tokyo Institute of Technology, Tokyo, Japan 163 Tomsk State University, Tomsk, Russia 164 Department of Physics, University of Toronto, Toronto, ON, Canada 165 (a) TRIUMF, Vancouver, BC; (b) Department of Physics and Astronomy, York University, Toronto, ON, Canada 166 Division of Physics and Tomonaga Center for the History of the Universe, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Japan 167 Department of Physics and Astronomy, Tufts University, Medford, MA, United States of America 168 Department of Physics and Astronomy, University of California Irvine, Irvine, CA, United States of America 169 Department of Physics and Astronomy, University of Uppsala, Uppsala, Sweden 170 Department of Physics, University of Illinois, Urbana, IL, United States of America 171 Instituto de Física Corpuscular (IFIC), Centro Mixto Universidad de Valencia – CSIC, Valencia, Spain 172 Department of Physics, University of British Columbia, Vancouver, BC, Canada 173 Department of Physics and Astronomy, University of Victoria, Victoria, BC, Canada 174 Fakultät für Physik und Astronomie, Julius-Maximilians-Universität Würzburg, Würzburg, Germany 175 Department of Physics, University of Warwick, Coventry, United Kingdom 176 Waseda University, Tokyo, Japan 177 Department of Particle Physics, Weizmann Institute of Science, Rehovot, Israel 178 Department of Physics, University of Wisconsin, Madison, WI, United States of America 179 Fakultät für Mathematik und Naturwissenschaften, Fachgruppe Physik, Bergische Universität Wuppertal, Wuppertal, Germany 180 Department of Physics, Yale University, New Haven, CT, United States of America 181 Yerevan Physics Institute, Yerevan, Armenia a Also at Borough of Manhattan Community College, City University of New York, NY; United States of America. b Also at California State University, East Bay; United States of America. c Also at Centre for High Performance Computing, CSIR Campus, Rosebank, Cape Town; South Africa. d Also at CERN, Geneva; Switzerland. e Also at CPPM, Aix-Marseille Université, CNRS/IN2P3, Marseille; France. f Also at Département de Physique Nucléaire et Corpusculaire, Université de Genève, Genève; Switzerland. g Also at Departament de Fisica de la Universitat Autonoma de Barcelona, Barcelona; Spain. h Also at Departamento de Física, Instituto Superior Técnico, Universidade de Lisboa, Lisboa; Portugal. i Also at Department of Applied Physics and Astronomy, University of Sharjah, Sharjah; United Arab Emirates. j Also at Department of Financial and Management Engineering, University of the Aegean, Chios; Greece. k Also at Department of Physics and Astronomy, University of Louisville, Louisville, KY; United States of America. l Also at Department of Physics and Astronomy, University of Sheffield, Sheffield; United Kingdom. m Also at Department of Physics, California State University, Fresno CA; United States of America. n Also at Department of Physics, California State University, Sacramento CA; United States of America. o Also at Department of Physics, King’s College London, London; United Kingdom. p Also at Department of Physics, St. Petersburg State Polytechnical University, St. Petersburg; Russia. q Also at Department of Physics, Stanford University; United States of America. r Also at Department of Physics, University of Fribourg, Fribourg; Switzerland. s Also at Department of Physics, University of Michigan, Ann Arbor MI; United States of America. 252 The ATLAS Collaboration / Physics Letters B 796 (2019) 230–252 t Also at Giresun University, Faculty of Engineering, Giresun; Turkey. u Also at Graduate School of Science, Osaka University, Osaka; Japan. v Also at Hellenic Open University, Patras; Greece. w Also at Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest; Romania. x Also at II. Physikalisches Institut, Georg-August-Universität Göttingen, Göttingen; Germany. y Also at Institucio Catalana de Recerca i Estudis Avancats, ICREA, Barcelona; Spain. z Also at Institut für Experimentalphysik, Universität Hamburg, Hamburg; Germany. aa Also at Institute for Mathematics, Astrophysics and Particle Physics, Radboud University Nijmegen/Nikhef, Nijmegen; Netherlands. ab Also at Institute for Particle and Nuclear Physics, Wigner Research Centre for Physics, Budapest; Hungary. ac Also at Institute of Particle Physics (IPP); Canada. ad Also at Institute of Physics, Academia Sinica, Taipei; Taiwan. ae Also at Institute of Physics, Azerbaijan Academy of Sciences, Baku; Azerbaijan. af Also at Institute of Theoretical Physics, Ilia State University, Tbilisi; Georgia. ag Also at Instituto de Física Teórica de la Universidad Autónoma de Madrid; Spain. ah Also at Istanbul University, Dept. of Physics, Istanbul; Turkey. ai Also at Joint Institute for Nuclear Research, Dubna; Russia. aj Also at LAL, Université Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, Orsay; France. ak Also at Louisiana Tech University, Ruston LA; United States of America. al Also at LPNHE, Sorbonne Université, Paris Diderot Sorbonne Paris Cité, CNRS/IN2P3, Paris; France. am Also at Manhattan College, New York NY; United States of America. an Also at Moscow Institute of Physics and Technology State University, Dolgoprudny; Russia. ao Also at National Research Nuclear University MEPhI, Moscow; Russia. ap Also at Physics Dept, University of South Africa, Pretoria; South Africa. aq Also at Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Freiburg; Germany. ar Also at School of Physics, Sun Yat-sen University, Guangzhou; China. as Also at The City College of New York, New York NY; United States of America. at Also at The Collaborative Innovation Center of Quantum Matter (CICQM), Beijing; China. au Also at Tomsk State University, Tomsk, and Moscow Institute of Physics and Technology State University, Dolgoprudny; Russia. av Also at TRIUMF, Vancouver BC; Canada. aw Also at Universidad de Granada, Granada (Spain); Spain. ax Also at Universita di Napoli Parthenope, Napoli; Italy. ∗ Deceased.