Studies of the decays $B^{+}\to p\bar{p}{h}^{+}$ and observation of $B^{+}\to \bar{\mathrm{\Lambda }}(1520)p$

Dynamics and direct $C\mathrm{\P }$ violation in three-body charmless decays of charged $B$ mesons to a proton, an antiproton and a light meson (pion or kaon) are studied using data, corresponding to an integrated luminosity of 1.0${fb}^{-1}$, collected by the $LHCb$ experiment in $pp$ collisions at a center-of-mass energy of 7 TeV. Production spectra are determined as a function of Dalitz-plot and helicity variables. The forward-backward asymmetry of the light meson in the $p\bar{p}$ rest frame is measured. No significant $C\mathrm{\P }$ asymmetry in $B^{+}\to p\bar{p}{K}^{+}$ decay is found in any region of the Dalitz plane. We present the first observation of the decay $B^+ \to \kern 0.1em\bar{\kern -0.1em\Lambda}(1520)(\to K^+\bar p)p$nearthe$K^+\bar p$thresholdandmeasure$$\mathcal{B}$(B^+ \to \kern 0.1em\bar{\kern -0.1em\Lambda}(1520)p)=(3.9^{+1.0}_{-0.9} ($\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}$)\pm0.1 ($\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}$)\pm0.3 ($\mathrm{B}\mathrm{F}$))\times 10^{-7}$, where BF denotes the uncertainty on secondary branching fractions.