Measurement of the mixing-induced CP-violating phase Φ<inf>s</inf> in B0<inf>s</inf> 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 √ s = 7 TeV with the LHCb detector. A timedependent fit to the data yields a value of Φ<inf>s</inf> = -0.019+0.173+0.004 <inf>-0.174-0.003</inf> rad, consistent with the Standard Model expectation. No evidence of direct CP violation is found.
Aaij, R., van den Brand, J. F. J., Dettori, F., Ketel, T. J., Koopman, R., Lambert, R. W., ... LHCb, C. (2012). Measurement of the CP-violating phase phi(s) in (B)over-bar(s)(0) -> J/psi pi(+)pi(-) decays. Physics Letters B, 713(4-5), 378-386. https://doi.org/10.1016/j.physletb.2012.06.032