Observation of the decay $\hat{I}{›}_b^0\to p{K}^{-}\hat{I}{¼}^{+}\hat{I}{¼}^{-}$ and a search for $CP$ violation

Abstract

A search for $CP$ violation in the decay $\hat{I}{›}_b^0\to p{K}^{-}\hat{I}{¼}^{+}\hat{I}{¼}^{-}$ is presented. This decay is mediated by flavour-changing neutral-current transitions in the Standard Model and is potentially sensitive to new sources of $CP$ violation. The study is based on a data sample of proton-proton collisions recorded with the LHCb experiment, corresponding to an integrated luminosity of $3$ ${\mathrm{fb}}^{-1}$. The $\hat{I}{›}_b^0\to p{K}^{-}\hat{I}{¼}^{+}\hat{I}{¼}^{-}$ decay is observed for the first time, and two observables that are sensitive to different manifestations of $CP$ violation are measured, $\hat{I}”{\mathcal{A}}_{CP}\equiv {\mathcal{A}}_{CP}(\hat{I}{›}_b^0\to p{K}^{-}\hat{I}{¼}^{+}\hat{I}{¼}^{-})-{\mathcal{A}}_{CP}(\hat{I}{›}_b^0\to p{K}^{-}J/\ddot{I}ˆ)$ and $a_{CP}^{\hat{T}-odd}$, where the latter is based on asymmetries in the angle between the $\hat{I}{¼}^{+}\hat{I}{¼}^{-}$ and $p{K}^{-}$ decay planes. These are measured to be $\hat{I}”{\mathcal{A}}_{CP}=(-3.5\pm 5.0(stat)\pm 0.2(syst))\times 10^{-2}$, $a_{CP}^{\hat{T}-odd}=(1.2\pm 5.0(stat)\pm 0.7(syst))\times 10^{-2}$, and no evidence for $CP$ violation is found.

All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-059.html