Measurements of $B_c^+$ production and mass with the $B_c^+ \to J/\psi \pi^+$ decay

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Measurements of $B_c^+$ production and mass are performed with the decay mode $B_c^+ \to J/\psi \pi^+$ using 0.37 fb$^{-1}$ of data collected in $pp$ collisions at $\sqrt{s}=7$ TeV by the LHCb experiment. The ratio of the production cross-section times branching fraction between the $B_c^+ \to J/\psi \pi^+$ and the $B^+ \to J/\psi K^+$ decays is measured to be $(0.68 \pm 0.10 ({\rm stat.}) \pm 0.03 ({\rm syst.}) \pm 0.05 ({\rm lifetime}))$% for $B_c^+$ and $B^+$ mesons with transverse momenta $p_{\rm T}>4 $GeV/$c$ and pseudorapidities $2.5<\eta<4.5$. The $B_c^+$ mass is directly measured to be $6273.7 \pm 1.3 ({\rm stat.}) \pm 1.6 ({\rm syst.})$ MeV/$c^2$, and the measured mass difference with respect to the $B^+$ meson is $M(B_c^+)-M(B^+) = 994.6 \pm 1.3 ({\rm stat.}) \pm 0.6 ({\rm syst.})$ MeV/$c^2$.

Figures and captions

Invariant mass distributions of selected (a) $ B_c^+\rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \pi^+$ candidates and (b) $ B^+\rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K^+$ candidates, used in the production measurement. The fits to the data are superimposed.

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Fig1b.pdf [24 KiB]
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Invariant mass distribution of $ B_c^+\rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \pi^+$ decays, used in the mass measurement. The fit to the data is superimposed.

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Tables and captions

Systematic uncertainties (in $ {\mathrm{ Me V /}c^2} $) of the $B_c^+$ mass and mass difference $\Delta M = M( B _ c ^+ )-M( B ^+ )$.

Table_1.pdf [40 KiB]
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Created on 18 October 2019.