Measurement of the CP-violating phase \phi s in Bs->J/\psi\pi+\pi-   decays
  Measurement of the mixing-induced CP-violating phase phi_s in Bs decays is of prime importance in probing new physics. Here 7421 +/- 105 signal events from the dominantly CP-odd final state J/\psi pi+ pi- are selected in 1/fb of pp collision data collected at sqrt{s} = 7 TeV with the LHCb detector. A time-dependent fit to the data yields a value of phi_s=-0.019^{+0.173+0.004}_{-0.174-0.003} rad, consistent with the Standard Model expectation. No evidence of direct CP violation is found. 
LHCb collaboration: R. Aaij, C. Abellan Beteta, B. Adeva, M. Adinolfi,   C. Adrover, A. Affolder, Z. Ajaltouni, J. Albrecht,...
hep-ex