Evidence for the rare decay $B^{+}\to \bar{\hat{I}}›p\hat{I}{¼}^{+}\hat{I}{¼}^{-}$

Abstract

A search for the rare decay $B^{+}\to \bar{\hat{I}}›p\hat{I}{¼}^{+}\hat{I}{¼}^{-}$ is performed using proton-proton collision data recorded by the LHCb experiment at a center-of-mass energy of $\sqrt{s}=13$ TeV, corresponding to an integrated luminosity of 5.4 fb${}^{-}1$. An excess of events is found with respect to the background-only expectation, with a signal significance of 3.5 standard deviations, in the low invariant-mass region of $m(\bar{\hat{I}}›p)<2.8$ GeV/$c^2$. The branching fraction is measured to be ${\mathcal{B}}_{\mathrm{low}}(B^{+}\to \bar{\hat{I}}›p\hat{I}{¼}^{+}\hat{I}{¼}^{-})=\left(1.70_{-0.56}^{+0.65}(\mathrm{stat})\pm 0.17(\mathrm{syst})\pm 0.14(\mathrm{ext})\right)\times 10^{-8}$, where the last uncertainty is due to external inputs on $\mathcal{B}(B^{+}\to J/\ddot{I}ˆ\bar{\hat{I}}›p)\times \mathcal{B}(J/\ddot{I}ˆ\to \hat{I}{¼}^{+}\hat{I}{¼}^{-})$. With no significant signal observed in the high $m(\bar{\hat{I}}›p)$ region above 2.8 GeV/$c^2$, an upper limit is set to be ${\mathcal{B}}_{\mathrm{high}}(B^{+}\to \bar{\hat{I}}›p\hat{I}{¼}^{+}\hat{I}{¼}^{-})<2.8(3.7)\times 10^{-9}$ at the $90\%$ ($95\%$) confidence level.

All figures and tables, along with any supplementary material and additional information, are available at https://lhcb-glance.cern.ch/alcm/public/analysis/full-details/5370