Evidence for CP violation in B0→J/ψπ0 decays

Three-body B+→pp¯K+ and B+→pp¯π+ decays are studied using a data sample corresponding to an integrated luminosity of 3.0  fb−1 collected by the LHCb experiment in proton-proton collisions at center-of-mass energies of 7 and 8 TeV. Evidence of CP violation in the B+→pp¯K+ decay is found in regions of the phase space, representing the first measurement of this kind for a final state containing baryons. Measurements of the forward-backward asymmetry of the light meson in the pp¯ rest frame yield AFB(pp¯K+,mpp¯<2.85  GeV/c2)=0.495±0.012  (stat)±0.007  (syst) and AFB(pp¯π+,mpp¯<2.85  GeV/c2)=−0.409±0.033  (stat)±0.006  (syst). In addition, the branching fraction of the decay B+→Λ¯(1520)p is measured to be B(B+→Λ¯(1520)p)=(3.15±0.48  (stat)±0.07  (syst)±0.26  (BF))×10−7, where BF denotes the uncertainty on secondary branching fractions.