First evidence of direct CP violation in charmless two-body decays of Bs mesons

TL;DR

This paper presents the first evidence of direct CP violation in Bs meson decays and the first observation of CP violation in B0 decays at a hadron collider, using data from LHCb.

Contribution

It provides the first experimental evidence of CP violation in Bs meson decays and the first observation in B0 decays at a hadron collider, expanding understanding of CP violation.

Findings

Evidence of CP violation in Bs → Kπ decays with 3.3σ significance.

Observation of CP violation in B0 → Kπ decays with >6σ significance.

Quantitative measurements of CP asymmetries in both decay modes.

Abstract

Using a data sample corresponding to an integrated luminosity of 0.35 $\mathrm{fb}^{-1}$ collected by LHCb in 2011, we report the first evidence of CP violation in the decays of $B^0_s$ mesons to $K^\pm \pi^\mp$ pairs, $A_{CP}(B^0_s \rightarrow K \pi)=0.27 \pm 0.08\,\mathrm{(stat)} \pm 0.02\,\mathrm{(syst)}$, with a significance of 3.3$\sigma$. Furthermore, we report the first observation of CP violation in $B^0$ decays at a hadron collider, $A_{CP}(B^0 \rightarrow K\pi)=-0.088 \pm 0.011\,\mathrm{(stat)} \pm 0.008\,\mathrm{(syst)}$, with a significance exceeding 6$\sigma$.