Evidence for CP Violation in B+→p¯pK+ Decays

Abstract

Three-body B + → p ¯ p K + and B + → p ¯ p 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 C P violation in the B + → p ¯ p 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 p ¯ p rest frame yield A FB ( p ¯ p K + , m p ¯ p < 2.85 GeV / c 2 ) = 0.495 ± 0.012 ( stat ) ± 0.007 ( syst ) and A FB ( p ¯ p π + , m p ¯ p < 2.85 GeV / c 2 ) = − 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 ) ) × 1 0 − 7 , where BF denotes the uncertainty on secondary branching fractions.