Evidence for CP Violation in B^{+}pp[over ]K^{+} Decays

Three-body B^{+}pp[over ]K^{+} and B^{+}pp[over ]pi^{+} decays are studied using a data sample corresponding to an integrated luminosity of 3.0fb^{-1} collected by the LHCb experiment in proton-proton collisions at center-of-mass energies of 7 and 8TeV. Evidence of CP violation in the B^{+}pp[over ]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[over ] rest frame yield A_{FB}(pp[over ]K^{+},m_{pp[over ]}<2.85GeV/c^{2})=0.495±0.012(stat)±0.007(syst) and A_{FB}(pp[over ]pi^{+},m_{pp[over ]}<2.85GeV/c^{2})=-0.409±0.033(stat)±0.006(syst). In addition, the branching fraction of the decay B^{+}Lambda[over ](1520)p is measured to be B(B^{+}Lambda[over ](1520)p)=(3.15±0.48(stat)±0.07(syst)±0.26(BF))*10^{-7}, where BF denotes the uncertainty on secondary branching fractions.