LHCb searches for the strong CP-violating decays η → ππ and η′ → ππ

A search for the CP-violating strong decays η → π(+)π(−) and η′(958) → π(+)π(−) has been performed using approximately 2.5 × 10(7) events of each of the decays D(+) → π(+)π(+)π(−) and , recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0 fb(−)(1) of pp collision data recorded during LHC Run 1 and 0.3 fb(−)(1) recorded in Run 2. No evidence is seen for with η (()(′)()) → π(+)π(−) and upper limits at 90% confidence level are set on the branching fractions, and . The limit for the η decay is comparable with the existing one, while that for the η′ is a factor of three smaller than the previous limit.