# Search for the rare decay $\Lambda_{c}^{+} \to p\mu^+\mu^-$

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## Abstract

A search for the flavor-changing neutral-current decay $\Lambda_{c}^{+} \to p\mu^+\mu^-$ is reported using a data set corresponding to an integrated luminosity of $3.0\rm fb^{-1}$ collected by the LHCb collaboration. No significant signal is observed outside of the dimuon mass regions around the $\phi$ and $\omega$ resonances and an upper limit is placed on the branching fraction of $\mathcal{B} (\Lambda_{c}^{+} \to p\mu^+\mu^-) < 7.7 (9.6)\times 10^{-8} {\rm at} 90\% (95\%)$ confidence level. A significant signal is observed in the $\omega$ dimuon mass region for the first time.

## Figures and captions

 Mass distribution of $\Lambda ^+_ c \rightarrow p \mu ^+\mu ^-$ candidates in the $\phi$ region after the first BDT requirement. The solid line shows the result of the fit described in the text, while the dashed line indicates the background component. Lc2pPh[..].pdf [19 KiB] HiDef png [167 KiB] Thumbnail [151 KiB] The efficiency weights for $\Lambda ^+_ c \rightarrow p \mu ^+\mu ^-$ as a function of the dimuon invariant mass squared $m^{2}(\mu ^+\mu ^- )$ and by the invariant mass of the proton and the negatively charged muon squared $m^{2}( p \mu^-)$. The weights are normalized to the average efficiency. dalitz[..].pdf [14 KiB] HiDef png [106 KiB] Thumbnail [116 KiB] Mass distribution for selected $p$ $\mu ^+\mu ^-$ candidates in the three regions of the dimuon invariant mass: a) nonresonant region, b) $\phi$ region, c) $\omega$ region. The solid lines show the results of the fit as described in the text. The dashed lines indicate the background component. pmumu_[..].pdf [33 KiB] HiDef png [462 KiB] Thumbnail [454 KiB] Invariant mass distribution $m({\mu ^+\mu ^- })$ for $\Lambda ^+_ c \rightarrow p \mu ^+\mu ^-$ candidates with mass $\pm 25 {\mathrm{ Me V /}c^2}$ around the $\Lambda ^+_ c$ mass. The solid line shows the result of the fit, while the dashed line indicates the background component. Lc_mum[..].pdf [18 KiB] HiDef png [183 KiB] Thumbnail [140 KiB] The CL$_{\rm s}$ value as a function of the ${\cal B}(\Lambda ^+_ c \rightarrow p \mu ^+\mu ^- )$ branching fraction. The median expected value of an ensemble (assuming no signal component) is shown by the dashed line, with the $\pm 1\sigma$ and $\pm 2\sigma$ regions shaded. The observed distribution is shown by the solid line. Lc2pmu[..].pdf [17 KiB] HiDef png [177 KiB] Thumbnail [140 KiB] Animated gif made out of all figures. PAPER-2017-039.gif Thumbnail

## Tables and captions

 Systematic uncertainties on the efficiency ratio used in the determination of the branching fraction in the nonresonant and $\omega$ regions. Table_1.pdf [53 KiB] HiDef png [52 KiB] Thumbnail [27 KiB] tex code

Created on 24 August 2019.Citation count from INSPIRE on 24 August 2019.