Branching fraction measurement of the $\hat{I}›\to p\hat{I}{¼}^{-}\overline{\hat{I}}{½}_{\hat{I}}¼$ decay

Abstract

A measurement of the branching fraction for the decay $\hat{I}›\to p\hat{I}{¼}^{-}\overline{\hat{I}}{½}_{\hat{I}}¼$ is presented using $\text{pp}$ collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV. The analysis is based on data recorded between 2016 and 2018, corresponding to an integrated luminosity of $5.4{\text{fb}}^{-1}$. The result is obtained using $\hat{I}›\to p\ddot{I}{€}^{-}$ decays as a normalisation channel. The measured branching fraction is $B(\hat{I}›\to p\hat{I}{¼}^{-}\overline{\hat{I}}{½}_{\hat{I}}¼)=(1.462\pm 0.016\pm 0.100\pm 0.011)\times 10^{-4}$, where the uncertainties are statistical, systematic, and due to the limited knowledge of the normalisation mode branching fraction, respectively. This result improves the precision of the branching fraction measurement by a factor of two compared to the previous best measurement and sets a more stringent bound on lepton flavour universality in $s\to u$ quark transitions. It is consistent with previous measurements, and the extracted lepton flavour universality test observable, $R^{\hat{I}¼e}=\frac{\hat{I}“(\hat{I}›\to p\hat{I}{¼}^{-}\overline{\hat{I}}{½}_{\hat{I}}¼)}{\hat{I}“(\hat{I}›\to p{e}^{-}\overline{\hat{I}}{½}_e)}=0.175\pm 0.012$, agrees with the Standard Model prediction.

All figures and tables, along with any supplementary material and additional information, are available at https://lbfence.cern.ch/alcm/public/analysis/full-details/3735/ (LHCb public pages)