Search for C violation in the decay η → π0e+e with WASA-at-COSY

The WASA-at-COSY Collaboration

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We report on the search for the rare decay η→π0e+e which is of interest to study C violation in the electromagnetic interaction which would indicate contributions from physics beyond the Standard Model, since the allowed decay via a two-photon intermediate state is strongly suppressed. The experiment has been performed using the WASA-at-COSY installation, located at the COSY accelerator of the Forschungszentrum Jülich, Germany. In total 3×107 events of the reaction pd→3Heη have been recorded at an excess energy of Q=59.8MeV. Based on this data set the C parity violating decay η→π0γ→π0e+e via a single-photon intermediate state has been searched for, resulting in new upper limits of Γ(η→π0e+e)/Γ(η→π+ππ0)<3.28×10−5 and Γ(η→π0e+e)/Γ(η→all)<7.5×10−6 (CL=90%), respectively.

Original languageEnglish
Pages (from-to)378-384
Number of pages7
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Publication statusPublished - 10 Sep 2018




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