Evidence of CP violation in B+→pp¯K+ decays
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Abstract
Three-body $B^+\\to p \\overline p K^+$ and $B^+\\to p \\overline p \\pi^+$ 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 $B^+\\to p \\overline p K^+$ 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 $p\\overline p$ rest frame yield $A_{\\mathrm{FB}}(p \\overline p K^+,~m_{p\\overline p}<2.85\\mathrm{\\,Ge\\kern -0.1em V\\!/}c^2)=0.495\\pm0.012~(\\mathrm{stat})\\pm0.007~(\\mathrm{syst})$ and $A_{\\mathrm{FB}}(p\\overline p \\pi^+,~m_{p\\overline p}<2.85\\mathrm{\\,Ge\\kern -0.1em V\\!/}c^2)=-0.409\\pm0.033~(\\mathrm{stat})\\pm0.006~(\\mathrm{syst})$. In addition, the branching fraction of the decay $B^+\\to\\kern 0.1em\\overline{\\kern -0.1em\\Lambda}(1520)p$ is measured to be $\\mathcal{B}(B^+ \\to \\kern 0.1em\\overline{\\kern -0.1em\\Lambda}(1520)p)=(3.15\\pm0.48~(\\mathrm{stat})\\pm0.07~(\\mathrm{syst})\\pm0.26~(\\mathrm{BF}))\\times 10^{-7}$, where BF denotes the uncertainty on secondary branching fractions.