Measurement of the CP-violating phase ϕsφs in B0s→ J/π+π− in decays

Measurement of the mixing-induced CP-violating phase ϕs in decays is of prime importance in probing new physics. Here 7421±105 signal events from the dominantly CP-odd final state J/ψπ+π− are selected in 1 fb−1 of pp collision data collected at with the LHCb detector. A time-dependent fit to the data yields a value of , consistent with the Standard Model expectation. No evidence of direct CP violation is found