TY - JOUR

T1 - Measurement of η → π0γγ branching fraction with the KLOE detector

AU - The KLOE-2 Collaboration

AU - Солодов, Евгений Петрович

N1 - This work was supported in part by the Polish National Science Centre through the Grant No. 2017/26/M/ST2/00697 and the “Leverhulme Trust LIP-2021-014”. We warmly thank our former KLOE colleagues for the access to the data collected during the KLOE data taking campaign. We thank the DAΦNE team for their efforts in maintaining good running conditions and their collaboration during both the KLOE run [27] and the KLOE-2 data taking with an upgraded collision scheme [28, 29]. We are very grateful to our colleague G. Capon for his enlightening comments and suggestions about the manuscript. We want to thank our technical staff: M. Anelli for his continuous attention to the gas system and detector safety; A. Balla, M. Gatta, G. Corradi and G. Papalino for electronics maintenance; C. Piscitelli for his help during major maintenance periods. We sincerely thank the technical staff of the LNF computing and web service, S. Angius, R. Orrù, D. Spigone, and M. Tota, for their support in the maintenance of the KLOE Computing Center. We would like to express our gratitude to M. Pistoni for his help and technical support on computing, L. dell’Agnello, D. Cesini, and C. Pellegrino for their support in the KLOE/KLOE-2 data transfer at CNAF, A. Antonelli and M. Palutan, for their support while heading the LNF research division.

PY - 2026/1/15

Y1 - 2026/1/15

N2 - 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 B(η → π0γγ) is measured to be (0.98±0.11stat ±0.14syst)×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.

AB - 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 B(η → π0γγ) is measured to be (0.98±0.11stat ±0.14syst)×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.

KW - e +-e − Experiments

UR - https://www.scopus.com/pages/publications/105030972240

U2 - 10.1007/JHEP01(2026)091

DO - 10.1007/JHEP01(2026)091

M3 - Article

VL - 2026

JO - Journal of High Energy Physics

JF - Journal of High Energy Physics

SN - 1029-8479

IS - 1

M1 - 91

ER -