Assessment of the a2(1320) tensor-meson contribution to η=η' → π0γγ decays
Escribano, Rafel (Universitat Autònoma de Barcelona. Departament de Física)
Gonzàlez-Solís, Sergi (Universitat de Barcelona . Departament de Física Quàntica i Astrofísica)
Royo, Emilio (Institut de Física d'Altes Energies)

Date:	2025
Abstract:	In light of the recent measurement of the η → πγγ decay by the KLOE-2 Collaboration, a previous analysis including vector- and scalar-meson exchange contributions using the vector meson dominance and linear sigma model frameworks, respectively, is extended in the present study to incorporate the effects of the a2(1320) tensor meson within a chiral context. Although the individual contribution of the a2 is negligible, its destructive interference with the vector-meson resonances is found to be significant, representing approximately 18% of the total signal and substantially affecting the diphoton invariant-mass distribution, especially at low mγγ values. The total decay rate is calculated to be Γ(η → πγγ) = 0. 154(22) eV, which corresponds to a branching ratio of BR(η → πγγ) = 1. 17(17) × 10. This result is approximately 5σ below the reported value of the particle data group, 2. 55(22) × 10, while it is in very good agreement with the KLOE-2 measurement, 0. 98 (11stat) (14syst) × 10. In contrast, the total contribution of the a2 is found to be negligible in η →■ πγγ, as this process is completely dominated by the exchange of an on-shell ω vector resonance.
Grants:	European Commission 824093 Agencia Estatal de Investigación PID2023-146142NB-I00 Generalitat de Catalunya 2021/SGR-00649 Agencia Estatal de Investigación CEX2024-001442-S Agencia Estatal de Investigación PID2023-147112NB-C21 Agencia Estatal de Investigación CEX2024-001451-M Generalitat de Catalunya 2021/SGR-01095
Note:	Altres ajuts: CERCA Programme/Generalitat de Catalunya
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Published in:	Physical Review D, Vol. 112, Num. 11 (December 2025) , art. 114009, ISSN 2470-0029

DOI: 10.1103/y661-zt9k

10 p, 1.2 MB

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Research literature > UAB research groups literature > Research Centres and Groups (research output) > Experimental sciences > Institut de Física d’Altes Energies (IFAE)
Articles > Research articles
Articles > Published articles