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

TL;DR

This paper reports the most precise measurement of the CKM angle gamma using a novel, model-independent approach applied to datasets from BESIII and LHCb, combining quantum-correlated D decays and B decays.

Contribution

It introduces a new unbinned, model-independent method for measuring gamma, integrating data from BESIII and LHCb for improved precision.

Findings

Measured gamma as (71.3 ± 5.0) degrees

Achieved the most precise gamma measurement to date

Results are consistent with previous measurements and world averages

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 $C\!P$-violating phase $\gamma$ is determined from ${B^{\pm}\rightarrow D(\rightarrow K_{\rm S}^{0} h^{\prime+}h^{\prime-}) h^{\pm}}$ decays in LHCb data, where $h^{(\prime)}$ is either a pion or kaon, while the corresponding strong-phase parameters are measured using doubly tagged ${D\rightarrow K_{\rm S/L}^0 h^{\prime+} h^{\prime-}}$ 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 $C\!P$-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.