First observation of CP violation in the decays of Bs mesons

TL;DR

This paper reports the first observation of CP violation in Bs meson decays using LHCb data, providing a significant milestone in understanding matter-antimatter asymmetry.

Contribution

It presents the first measurement of CP violation in Bs meson decays and offers the most precise measurement for B0 decays, advancing experimental tests of the Standard Model.

Findings

First observation of CP violation in Bs mesons

Most precise measurement of CP violation in B0 decays

Significance exceeds five standard deviations

Abstract

Using pp collision data, corresponding to an integrated luminosity of $1.0 \mathrm{fb}^{-1}$, collected by LHCb in 2011 at a center-of-mass energy of 7 TeV, we report the measurement of direct CP violation in $B^0_s \to K^-\pi^+$ decays, $A_{C/!P}(B^0_s \rightarrow K^- \pi^+)=0.27 \pm 0.04\,\mathrm{(stat)} \pm 0.01\,\mathrm{(syst)}$, with significance exceeding five standard deviations. This is the first observation of CP violation in the decays of $B^0_s$ mesons. Furthermore, we provide an improved determination of direct CP violation in $B^0 \to K^+\pi^-$ decays, $A_{C/!P}(B^0\rightarrow K^+ \pi^-)=-0.080 \pm 0.007\,\mathrm{(stat)} \pm 0.003\,\mathrm{(syst)}$, which is the most precise measurement of this quantity to date.