Measurement of relative branching fractions of B decays to $\psi(2S)$ and $J/\psi$ mesons

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The relative rates of B-meson decays into $J/\psi$ and $\psi(2S)$ mesons are measured for the three decay modes in pp collisions recorded with the LHCb detector. The ratios of branching fractions ($\mathcal{B}$) are measured to be $\frac{\mathcal{B}(B^+ \to \psi(2S) K^+)}{\mathcal{B}(B^+ \to J/\psi K^+)} = 0.594 \pm 0.006 (stat) \pm 0.016 (syst) \pm 0.015 (R_{\psi})$, $\frac{\mathcal{B}(B^0 \to \psi(2S) K^{*0})}{\mathcal{B}(B^0 \to J/\psi K^{*0})} = 0.476 \pm 0.014 (stat) \pm 0.010 (syst) \pm 0.012 (R_{\psi})$, $\frac{\mathcal{B}^{0}_{s}(B^0_s \to \psi(2S)\phi)}{\mathcal{B}(B^0_s \to J/\psi\phi)} = 0.489 \pm 0.026 (stat) \pm 0.021 (syst) \pm 0.012 (R_{\psi})$ where the third uncertainty is from the ratio of the $\psi(2S)$ and $J/\psi$ branching fractions to $\mu\mu$.

Figures and captions

Mass distributions of (a) $ B ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ $, (b) $ B ^+ \rightarrow \psi(2S) K ^+ $, (c) $ B ^0 \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ \pi ^- $, (d) $ B ^0 \rightarrow \psi(2S) K ^+ \pi ^- $, (e) $ B ^0_ s \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ K ^- $ and (f) $ B ^0_ s \rightarrow \psi(2S) K ^+ K ^- $. The total fitted function (solid) and the combinatorial background (dashed) are shown. The variation in resolution of the different modes is fully consistent with the energy released in the decays and in agreement with simulation.

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Tables and captions

Summary of the signal yields for the six $ B $ modes considered and the ratios of the number of $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} $ and $\psi(2S)$ decays: $N^{\rm{total}}$ is the summed signal yield for resonant and non-resonant modes, $N^{\rm{non-res}}$ is the signal yield for non-resonant modes only and $N^{\rm{res}}_{\psi X}$ is the signal yield for resonant decays (through $ K ^{*0}$ or $\phi$). The uncertainties are statistical only.

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Systematic uncertainties (in %) on the relative branching fractions.

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Created on 05 March 2021.