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Search for $B_c^+$ decays to the $p\overline p\pi^+$ final state

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Abstract

A search for the decays of the $B_c^+$ meson to $p\bar p\pi^+$ is performed for the first time using a data sample corresponding to an integrated luminosity of 3.0 $\mathrm{fb}^{-1}$ collected by the LHCb experiment in $pp$ collisions at centre-of-mass energies of $7$ and $8$ TeV. No signal is found and an upper limit, at 95% confidence level, is set, $\frac{f_c}{f_u}\times\mathcal{B}(B_c^+\to p\bar p\pi^+)<3.6\times10^{-8}$ in the kinematic region $m(p\bar p)<2.85\mathrm{\,GeV\!/}c^2$, $p_{\rm T}(B)<20\mathrm{\,GeV\!/}c$ and $2.0<y(B)<4.5$, where $\mathcal{B}$ is the branching fraction and $f_c$ ($f_u$) is the fragmentation fraction of the $b$ quark into a $B_c^+$ ($B^+$) meson.

Figures and captions

Distributions of BDT output for the $ B _ c ^+ \rightarrow p \overline{p} \pi^{+}$ signal and the background. The vertical dashed lines indicate the lower limits of the three regions in which the signal is determined.

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Fits to the $ p \overline p \pi ^+ $ invariant mass in the $ B ^+$ region, for (left) $m( p \overline p )<2.85 {\mathrm{\,GeV\!/}c^2} $ and (right) $2.85<m( p \overline p )<3.15 {\mathrm{\,GeV\!/}c^2} $. The blue dashed, red long-dashed and green dotted-dashed lines represent the signal, combinatorial background and partially reconstructed background components, respectively. The error bars show 68% Poisson confidence level intervals.

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Projection of fits to the $ p \overline p \pi ^+ $ invariant mass in the $ B _ c ^+$ region, in the bins of BDT output (top) $0.04<X<0.12$, (middle) $0.12<X<0.18$ and (bottom) $X>0.18$, for (left) $m( p \overline p )<2.85 {\mathrm{\,GeV\!/}c^2} $ and (right) $2.85<m( p \overline p )<3.15 {\mathrm{\,GeV\!/}c^2} $. The red long-dashed lines represent the combinatorial background. The signal and partially reconstructed components are too small to be shown.

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Combined acceptance in the plane $(m^2( p \overline p ),m^2( p \pi))$ for (left) $ B _ c ^+ \rightarrow p \overline{p} \pi^{+}$ and (right) $ B ^+ \rightarrow p \overline{p} \pi^{+}$ events. The vertical dashed line corresponds to $m( p \overline p )=2.85 {\mathrm{\,GeV\!/}c^2} $.

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$p$-value profile for (left) $R_p$ and (right) $R_p^ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} $. The horizontal red solid and dashed lines indicate the 5% and 10% confidence levels.

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Animated gif made out of all figures.

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Tables and captions

Relative systematic uncertainties (in %) on the ratio $\epsilon_u/\epsilon_c$ and input branching fractions.

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Created on 11 December 2018.Citation count from INSPIRE on 11 December 2018.