Measurement of η → π⁰γγ branching fraction with the KLOE detector

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Babusci, D, Beltrame, P ORCID: 0000-0001-9523-6128, Berlowski, M, Bloise, C, Bossi, F, Branchini, P, Cao, B, Ceradini, F, Ciambrone, P, Cotrozzi, L ORCID: 0000-0002-0375-0611 et al (show 43 more authors) , Curciarello, F, Czerwinski, E, D'agostini, G, D'amico, R, Dane, E, De Leo, V, De Lucia, E, De Santis, A, De Simone, P, Di Domenico, A, Diociaiuti, E, Domenici, D, D'uffizi, A, Fantini, G, Fiore, S, Gajos, A, Gamrat, S, Gauzzi, P, Giovannella, S, Graziani, E, Ignatov, F ORCID: 0000-0001-7061-6060, Kang, X, Kupsc, A, Mandaglio, G, Martini, M, Miscetti, S, Moskal, P, Passeri, A, Patera, V, Perez Del Rio, E, Punzi, L, Sborzacchi, F, Schioppa, M, Selce, A, Silarski, M, Sirghi, F, Solodov, EP, Teubner, T ORCID: 0000-0002-0680-0776, Venanzoni, G ORCID: 0000-0002-3525-476X, Vestergaard, N, Wislicki, W, Wolke, M and Zaid, E (2026) Measurement of η → π⁰γγ branching fraction with the KLOE detector JOURNAL OF HIGH ENERGY PHYSICS, 2026 (1). 91-. ISSN 1126-6708, 1029-8479

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Abstract

We present a measurement of the doubly radiative decay η → π⁰γγ based on a sample of 82 million η mesons produced in the e⁺e⁻ → ϕ → ηγ process at the Frascati ϕ-factory DAΦNE. From the data analysis, 1246 ± 133 signal events were observed. By normalising the signal to the well-known η → 3π⁰ decay the branching fraction is measured to be (0.98 ± 0.11<inf>stat</inf> ± 0.14<inf>syst</inf>) × 10⁻⁴. This result agrees with a preliminary KLOE measurement, but is a factor of two smaller than the current world average. Results for dΓ(η → π⁰γγ)/dM²(γγ) are also presented and compared with the latest theoretical predictions.

Item Type:	Article
Uncontrolled Keywords:	<italic>e</italic>(+)-<italic>e</italic>(<italic>-</italic>) Experiments
Divisions:	Faculty of Science & Engineering Faculty of Science & Engineering > School of Physical Sciences Faculty of Science & Engineering > School of Physical Sciences > Mathematical Sciences Faculty of Science & Engineering > School of Physical Sciences > Physics
Depositing User:	Symplectic Admin
Date Deposited:	02 Jun 2026 07:44
Last Modified:	16 Jun 2026 04:00
DOI:	10.1007/JHEP01(2026)091
Open Access URL:	https://doi.org/10.1007/JHEP01(2026)091
Related Websites:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3198709
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