Upper limit on the η → π + π − branching fraction with the KLOE experiment
- Babusci D.
- Berlowski M.
- Bloise C.
- Bossi F.
- Branchini P.
- Budano A.
- Cao B.
- Ceradini F.
- Ciambrone P.
- Curciarello F.
- Czerwinski E.
- D'Agostini G.
- Dane E.
- De Leo V.
- De Lucia E.
- De Santis A.
- De Simone P.
- Di Cicco A.
- Di Domenico A.
- Domenici D.
- D'Uffizi A.
- Fantini A.
- Fermani P.
- Fiore S.
- Gajos A.
- Gauzzi P.
- Giovannella S.
- Graziani E.
- Ivanov V. L.
- Johansson T.
- Kang X.
- Kisielewska-Kaminska D.
- Kozyrev E. A.
- Krzemien W.
- Kupsc A.
- Lukin P. A.
- Mandaglio G.
- Martini M.
- Messi R.
- Miscetti S.
- Moricciani D.
- Moskal P.
- Parzych S.
- Passeri A.
- Patera V.
- Perez del Rio E.
- Santangelo P.
- Schioppa M.
- Selce A.
- Silarski M.
- Sirghi F.
- Solodov E. P.
- Tortora L.
- Venanzoni G.
- Wislicki W.
- Wolke M.
Publication date
January 2020
DOI Publisher
Springer Science and Business Media LLCAbstract
Based on an integrated luminosity of 1.61 fb−1e+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
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