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First observation of a baryonic $B_s^0$ decay

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Abstract

We report the first observation of a baryonic $B_s^0$ decay, $B_s^0 \to p \overline{\Lambda} K^-$, using proton-proton collision data recorded by the LHCb experiment at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of $3.0\,\mathrm{fb}^{-1}$. The branching fraction is measured to be $ \mathcal{B}(B_s^0 \to p \overline{\Lambda} K^-) + \mathcal{B}(B_s^0 \to \bar{p} \Lambda K^+) = \left[5.46 \pm 0.61 \pm 0.57 \pm 0.50 (\mathcal{B}) \pm 0.32 (f_s/f_d)\right]\times 10^{-6}, $ where the first uncertainty is statistical and the second systematic, the third uncertainty accounts for the experimental uncertainty on the branching fraction of the $B^0 \to p \overline{\Lambda} \pi^-$ decay used for normalization, and the fourth uncertainty relates to the knowledge of the ratio of $b$-quark hadronization probabilities $f_s/f_d$.

Figures and captions

Mass distributions for $b$-hadron candidates for (left) the $ p \overline{\Lambda} \pi ^- $ and (right) the $ p \overline{\Lambda} K ^- $ sample for the combined long and downstream categories. The black points represent the data, the solid blue curve the result of the fit, the red dashed curve the $ B ^0_ s \!\rightarrow p \overline{\Lambda} K ^- $ contribution, the black (magenta) dotted curve the $ B ^0 \!\rightarrow p \overline{\Lambda} \pi ^- $ ( $ B ^0_ s \!\rightarrow p \overline \Sigma {}^0 K ^- $ ) and the green dash-dotted curve the contribution from $ B ^0 \!\rightarrow p \overline \Sigma {}^0 \pi ^- $ decays. The combinatorial background distribution is indicated by the shaded histogram.

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Efficiency-corrected and background-subtracted $m( p \overline{\Lambda} )$ invariant mass distributions for (left) $ B ^0 \!\rightarrow p \overline{\Lambda} \pi ^- $ and (right) $ B ^0_ s \!\rightarrow p \overline{\Lambda} K ^- $ candidates. The distributions are normalized to unity.

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Supplementary Material [file]

Supplementary material full pdf

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This ZIP file contains supplemetary material for the publication LHCb-PAPER-2017-012. The files are: README : this README file supplementary.pdf : An overview of the extra figures and tables *.pdf, *.png, *.eps : The figures in various formats

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Created on 18 December 2018.Citation count from INSPIRE on 18 December 2018.