A baryonic decay of the $B_c^+$ meson, $B_c^+\to J/\psi p\overline{p}\pi^+$, is observed for the first time, with a significance of $7.3$ standard deviations, in $pp$ collision data collected with the LHCb detector and corresponding to an integrated luminosity of $3.0$ fb$^{1}$ taken at centerofmass energies of $7$ and $8$ $\mathrm{TeV}$. With the $B_c^+\to J/\psi \pi^+$ decay as normalization channel, the ratio of branching fractions is measured to be \begin{equation*} \frac{\mathcal{B}(B_c^+\to J/\psi p\overline{p}\pi^+)}{\mathcal{B}(B_c^+\to J/\psi \pi^+)} = 0.143^{\,+\,0.039}_{\,\,0.034}\,(\mathrm{stat})\pm0.013\,(\mathrm{syst}). \end{equation*} The mass of the $B_c^+$ meson is determined as $M(B_c^+)=6274.0\pm1.8\,(\mathrm{stat})\pm0.4\,(\mathrm{syst})\,\mathrm{MeV}/c^2$, using the $B_c^+\to J/\psi p\overline{p}\pi^+$ channel.
Invariant mass distribution for (left) $ B _ c ^+ \!\rightarrow { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} p \overline{p}\pi ^+ $ and (right) $ B _ c ^+ \!\rightarrow { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} \pi ^+ $ candidates. The superimposed curves show the fitted contributions from signal (dashed), combinatorial background (dotted), misidentification background (dotdashed) and their sum (solid). 
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Invariant mass distributions of (left) $M(p\overline{p})$ and (right) $M(p\pi ^+ )$ for data (dots) and simulation (solid) using uniform phasespace model, for $ B _ c ^+ \!\rightarrow { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} p \overline{p}\pi ^+ $ decay. 
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Animated gif made out of all figures. 
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Systematic uncertainties for the $ B _ c ^+ $ mass measurement. 
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Systematic uncertainties (in percent) for the relative branching fraction measurement. 
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Supplementary material full pdf 
supple[..].pdf [92 KiB] 

This ZIP file contains supplemetary material for the publication LHCbPAPER2014039. The files are: Supplementary.pdf : Decribing the thee LHCb measurements of Bc+ mass, and their average. *.pdf, *.png, *.eps, *.C : The results Bc+ mass measurements in variuous formats supp.tex: main latex file used to produce supplementary.pdf, including mass result table 
bcComp.pdf [4 KiB] HiDef png [195 KiB] Thumbnail [64 KiB] *C file 
Created on 16 February 2019.Citation count from INSPIRE on 21 February 2019.