Upper limit on the η → π + π − branching fraction with the KLOE experiment
oleh: The KLOE-2 collaboration, D. Babusci, M. Berlowski, C. Bloise, F. Bossi, P. Branchini, A. Budano, B. Cao, F. Ceradini, P. Ciambrone, F. Curciarello, E. Czerwiński, G. D’Agostini, E. Danè, V. De Leo, E. De Lucia, A. De Santis, P. De Simone, A. Di Cicco, A. Di Domenico, D. Domenici, A. D’Uffizi, A. Fantini, P. Fermani, S. Fiore, A. Gajos, P. Gauzzi, S. Giovannella, E. Graziani, V. L. Ivanov, T. Johansson, X. Kang, D. Kisielewska-Kamińska, E. A. Kozyrev, W. Krzemien, A. Kupsc, P. A. Lukin, G. Mandaglio, M. Martini, R. Messi, S. Miscetti, D. Moricciani, P. Moskal, S. Parzych, A. Passeri, V. Patera, E. Perez del Rio, P. Santangelo, M. Schioppa, A. Selce, M. Silarski, F. Sirghi, E. P. Solodov, L. Tortora, G. Venanzoni, W. Wiślicki, M. Wolke
| Format: | Article |
|---|---|
| Diterbitkan: | SpringerOpen 2020-10-01 |
Deskripsi
Abstract Based on an integrated luminosity of 1.61 fb −1 e + e − collision data collected with the KLOE detector at DAΦNE, the Frascati ϕ-factory, a search for the P- and CP-violating decay η → π + π − has been performed. Radiative ϕ → ηγ decay is exploited to access the η mesons. No signal is observed in the π + π − invariant mass spectrum, and the upper limit on the branching fraction at 90% confidence level is determined to be ℬ(η → π + π − ) < 4.9 × 10 −6, which is approximately three times smaller than the previous KLOE result. From the combination of these two measurements we get ℬ(η → π + π − ) < 4.4 × 10 −6 at 90% confidence level.