Dynamics and direct $C\P$ violation in threebody 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 centerofmass energy of 7 TeV. Production spectra are determined as a function of Dalitzplot and helicity variables. The forwardbackward asymmetry of the light meson in the $p\bar p$ rest frame is measured. No significant $C\P$ 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 $B^+ \to \bar{\Lambda}(1520)(\to K^+\bar p)p$ near the $K^+\bar p$ threshold and measure $\mathcal{B}(B^+ \to \bar{\Lambda}(1520)p)=(3.9^{+1.0}_{0.9} (\mathrm{stat})\pm0.1 (\mathrm{syst})\pm0.3 (\mathrm{BF}))\times 10^{7}$, where BF denotes the uncertainty on secondary branching fractions.
Leading tree and penguin diagrams for $ B^+ \rightarrow p \overline p h^+$ decays. 
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Invariant mass distributions of (left) $p\overline p K ^+ $ and (right) $p\overline p \pi ^+ $ candidates. The points with error bars represent data. The solid black line represents the total fit function. Blue dashed, purple dotted, red longdashed and green dasheddotted curves represent the signal, crossfeed, combinatorial background and partially reconstructed background, respectively. 
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Efficiencycorrected differential yield as a function of $m_{p\overline p }$ for (left) $ B^+ \rightarrow p \overline p K ^+ $ and (right) $ B^+ \rightarrow p \overline p \pi ^+ $ . The data points are shown with their statistical and total uncertainties. For comparison, the solid lines represent the expectations for a uniform phase space production, normalized to the efficiencycorrected area. 
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Efficiencycorrected differential yield as a function of $m_{Kp}^2$ for $ B^+ \rightarrow p \overline p K ^+ $ . The data points are shown with their statistical and total uncertainties. The solid line represents the expectation for a uniform phase space production, normalized to the efficiencycorrected area, for comparison. 
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Efficiencycorrected differential yields as functions of $\cos\theta_p$ for (left) $ B^+ \rightarrow p \overline p K ^+ $ and (right) $ B^+ \rightarrow p \overline p \pi ^+ $ modes, after subtraction of the charmonium contributions. The data points are shown with their statistical and total uncertainties. 
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Signal weighted Dalitzplot distributions for (left) $ B^+ \rightarrow p \overline p K ^+ $ and (right) $ B^+ \rightarrow p \overline p \pi ^+ $ . Also shown are the iso$\cos\theta_p$ lines corresponding to the $\cos\theta_p$ bin boundaries; $\cos\theta_p=1$ (+1) is the uppermost (lowermost) line. The distributions are not corrected for efficiency. 
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Distribution of $ A_{ C P }$ for the Dalitzplot projections on $m_{p\overline p }$ and $m_{Kp}^2$ for $ B ^\pm \rightarrow p \overline p K^{\pm}$ events. In the $m_{p\overline p }$ projection (left), the bin $[2.85,3.15] {\mathrm{ Ge V /}c^2} $ contains only the value of the charmless $p\overline p K ^\pm $ after subtraction of the $\eta _ c $  $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu}$ contribution. The $m_{Kp}^2$ projection (right) has been obtained after removing the charmonia bands. 
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Invariant mass $m_{Kp}$ for the $ B^+ \rightarrow p \overline p K ^+ $ candidates near threshold. 
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Fit to the $B$ signal weighted $m_{Kp}$ distribution. 
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Projections of (left) $m_{Kp}$ and (right) $m_{p\overline p K ^+ }$ of the two dimensional fit used to obtain the $ B^+ \rightarrow \overline{\Lambda} (1520)p$ signal yield. 
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Animated gif made out of all figures. 
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Fitted $ B^+ \rightarrow p \overline p K ^+ $ signal yield, including the charmonium modes, efficiency and relative systematic uncertainty, in bins of $p\overline p $ invariant mass. The error on the efficiency includes all the sources of uncertainty. 
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Fitted $ B^+ \rightarrow p \overline p \pi ^+ $ signal yield, including the $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu}$ mode, $ B^+ \rightarrow p \overline p K ^+ $ crossfeed yield, signal efficiency, and relative systematic uncertainty in bins of $p\overline p $ invariant mass. 
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Yields, efficiencies and relative systematic uncertainties of the charmonium modes from the combined $(m_{p\overline p h^+},m_{p\overline p })$ fits for the regions $m_{p\overline p }\in[2.85,3.15] {\mathrm{ Ge V /}c^2} $ (for both $ B^+ \rightarrow p \overline p K ^+ $ and $ B^+ \rightarrow p \overline p \pi ^+ $ ) and $[3.60,3.75] {\mathrm{ Ge V /}c^2} $ (for $ B^+ \rightarrow p \overline p K ^+ $ ). 
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Fitted $ B^+ \rightarrow p \overline p K ^+ $ yields after subtracting the charmonium bands, efficiencies and relative systematic uncertainties in bins of $Kp$ invariant mass squared. 
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Fitted $ B^+ \rightarrow p \overline p K ^+ $ yields, efficiencies and relative systematic uncertainties in bins of $\cos\theta_{p}$. 
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Fitted $ B^+ \rightarrow p \overline p \pi ^+ $ signal yields, efficiencies and relative systematic uncertainties in bins of $\cos\theta_{p}$. 
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Systematic uncertainties for the $\mathcal{B}( B ^+ \rightarrow \overline{\Lambda} (1520)(\rightarrow K^+\overline p )p)/\mathcal{B}( B ^+ \rightarrow { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} (\rightarrow p\overline p ) K ^+ )$ branching fraction ratio. The total uncertainty is the sum in quadrature of the individual sources. 
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Created on 21 October 2019.