Precise measurement of the CKM angle $\gamma$ with a novel approach

Abstract

A measurement of the CKM angle $\gamma$ is performed by applying a novel, unbinned, model-independent approach to datasets of electron-positron collisions collected by the BESIII experiment and proton-proton collisions by the LHCb experiment, corresponding to integrated luminosities of 8 fb${}^{-1}$ and 9 fb${}^{-1}$, respectively. The $CP$-violating phase $\gamma$ is determined from $B^{\pm }\to D(\to K_{\mathrm{S}}^0{h}^{\prime +}{h}^{\prime -})h^{\pm }$ decays in LHCb data, where $h^{(\prime )}$ is either a pion or kaon, while the corresponding strong-phase parameters are measured using doubly tagged $D\to K_{S/L}^0{h}^{\prime +}{h}^{\prime -}$ decays in the quantum-correlated $D\overline{D}$ system present in BESIII data. A joint fit to both datasets, which allows for a simultaneous determination of the associated $CP$-violating observables and strong-phase parameters, yields $\gamma =(71.3\pm 5.0{)}^{\circ }$. The result is the most precise to date and consistent with previous measurements and world averages.

All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://lbfence.cern.ch/alcm/public/analysis/full-details/5991/ (LHCb public pages)