Measurement of the CKM angle ${\hat{I}}^3$ in $B^{\pm }\to D(\to K_{\mathrm{S}}^0{h}^{\prime +}{h}^{\prime -})h^{\pm }$ decays with a novel approach

Abstract

A measurement of the CKM angle ${\hat{I}}^3$ and related strong-phase parameters is performed using a novel, model-independent approach in $B^{\pm }\to D(\to K_{\mathrm{S}}^0{h}^{\prime +}{h}^{\prime -})h^{\pm }$ decays, where $h^{(\prime )}\equiv \ddot{I}€,K$. The analysis uses a joint data sample of electron-positron collisions collected by the BESIII experiment at the Beijing Electron-Positron Collider II during 2010--2011 and 2021--2022, corresponding to an integrated luminosity of 8 fb${}^{-1}$, and proton-proton collisions collected by the LHCb experiment at the Large Hadron Collider during 2011--2018, corresponding to an integrated luminosity of 9 fb${}^{-1}$. The two datasets are analyzed simultaneously by applying per-event weights based on the amplitude variation over the $D$-decay phase space to enhance the sensitivity to $CP$-violating observables. The CKM angle ${\hat{I}}^3$ is determined to be ${\hat{I}}^3=(71.3\pm 5.0{)}^{\circ }$, which constitutes the most precise single measurement to date.

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/3989/ (LHCb public pages)