Search for resonance-enhanced $CP$ and angular asymmetries in the $\Lambda^+_{c}\to p\mu^+\mu^-$ decay at LHCb

TL;DR

This paper reports the first measurement of $CP$ asymmetries and forward-backward asymmetries in $ ext{Lambda}_c^+ o p \, extmu^+ extmu^-$ decays using LHCb data, finding results consistent with Standard Model predictions.

Contribution

It provides the first experimental measurement of $CP$ and angular asymmetries in this decay channel, testing $CP$ symmetry and the Standard Model.

Findings

Measured $A_{CP}$, $ ext{Sigma} A_{FB}$, and $ ext{Delta} A_{FB}$ with uncertainties.

Results are consistent with $CP$ conservation and Standard Model.

First such measurement in this decay mode.

Abstract

The first measurement of the $CP$ asymmetry of the decay rate ($A_{CP}$) and the $CP$ average ($\Sigma A_{\text{FB}}$) and $CP$ asymmetry ($\Delta A_{\text{FB}}$) of the forward-backward asymmetry in the muon system of $\mathit{\Lambda}^+_c\to p\mu^+\mu^-$ decays is reported. The measurement is performed using a data sample of proton-proton collisions, recorded by the LHCb experiment from 2016 to 2018 at a center-of-mass energy of 13$\text{ TeV}$, which corresponds to an integrated luminosity of 5.4$\text{ fb}^{-1}$. The asymmetries are measured in two regions of dimuon mass near the $\phi$-meson mass peak. The dimuon-mass integrated results are \begin{align*} A_{CP} &= (-1.1 \pm 4.0 \pm 0.5)\%,\\ \Sigma A_{\text{FB}} &= (\phantom{-}3.9 \pm 4.0 \pm 0.6)\%,\\ \Delta A_{\text{FB}} &= (\phantom{-}3.1 \pm 4.0 \pm 0.4)\%, \end{align*} where the first uncertainty is statistical and the second systematic. The results are consistent with the conservation of $CP$ symmetry and the Standard Model expectations.