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Observation of the suppressed decay $\Lambda^{0}_{b}\rightarrow p\pi^{-}\mu^{+}\mu^{-}$

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Abstract

The suppressed decay $\Lambda^{0}_{b}\rightarrow p\pi^{-}\mu^{+}\mu^{-}$, excluding the $J/\psi$ and $\psi(2S)\rightarrow \mu^{+}\mu^{-}$ resonances, is observed for the first time with a significance of 5.5 standard deviations. The analysis is performed with proton-proton collision data corresponding to an integrated luminosity of $3\mathrm{fb}^{-1}$ collected with the LHCb experiment. The $\Lambda^{0}_{b}\rightarrow p\pi^{-}\mu^{+}\mu^{-}$ branching fraction is measured relative to the $\Lambda^{0}_{b}\rightarrow J/\psi(\rightarrow \mu^{+}\mu^{-})p\pi^{-}$ branching fraction giving \begin{align} \nonumber \frac{\mathcal{B}(\Lambda^{0}_{b}\rightarrow p\pi^{-}\mu^{+}\mu^{-})}{\mathcal{B}({\Lambda^{0}_{b}\rightarrow J/\psi(\rightarrow \mu^{+}\mu^{-})p\pi^{-}})} &= 0.044\pm0.012\pm0.007, \end{align} where the first uncertainty is statistical and the second is systematic. This is the first observation of a $b\rightarrow d$ transition in a baryonic decay.

Figures and captions

One of the lowest-order diagrams for the decay $\Lambda ^0_ b \!\rightarrow p \pi ^- \mu ^+\mu ^- $ .

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Mass distribution of $\Lambda ^0_ b \!\rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} p \pi ^- $ candidates compared to the result of the fit. The fit parameterisation is described in the text.

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Fig2.pdf

Mass distribution of $\Lambda ^0_ b \!\rightarrow p \pi ^- \mu ^+\mu ^- $ candidates compared to the result of the fit. The fit parameterisation is described in the text.

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Fig3.pdf

Animated gif made out of all figures.

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Tables and captions

Summary of the systematic uncertainties on the $\Lambda ^0_ b \!\rightarrow p \pi ^- \mu ^+\mu ^- $ branching fraction.

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tex code
Table_1.pdf

Supplementary Material [file]

This ZIP file contains supplementary material for the publication LHCb-PAPER-2016-049. The files are: Fig1-S.pdf Fig2-S.pdf

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Fig2-S.pdf [14 KiB]
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Created on 09 December 2018.Citation count from INSPIRE on 09 December 2018.