$CP$ violation in $B_s^0$ decays at LHCb

TL;DR

This paper reports the most precise measurements to date of $CP$ violation phases in $B_s^0$ decays using LHCb data, providing key insights into matter-antimatter asymmetry and testing the Standard Model.

Contribution

It presents the first high-precision measurements of $CP$-violating phases in $b\to c\bar{c}s$ and $b\to s\bar{s}s$ transitions using LHCb Run I data, improving the understanding of $CP$ violation.

Findings

Most precise measurement of $\phi_s^{c\bar{c}s}$: 0.070 ± 0.068 (stat) ± 0.008 (syst) rad.

Most accurate measurement of $\phi_s^{s\bar{s}s}$: -0.17 ± 0.15 (stat) ± 0.03 (syst) rad.

Large data sample: 27,000 $B_s^0\to J/\psi \pi^+\pi^-$ and 4,000 $B_s^0\to \phi\phi$ events.

Abstract

Latest LHCb measurements of $CP$ violation in the interference between mixing and decay are presented based on $pp$ collision data collected during LHC Run I, corresponding to an integrated luminosity of $3.0\, {\rm fb}^{-1}$. Approximately $27\, 000$ $B_s^0\to J/\psi \pi^+\pi^-$ signal events are used to make what is at the moment the most precise single measurement of the $CP$-violating phase in $b\to c\bar{c}s$ transitions, $\phi_s^{c\bar{c}s}=0.070\pm0.068{\rm (stat.)}\pm0.008{\rm (syst.)}$ rad. The most accurate measurement of the $CP$-violating phase in $b\to s\bar{s}s$ transitions, $\phi_s^{s\bar{s}s}$, is found from approximately $4\, 000$ $B_s^0\to \phi\phi$ signal events to be $\phi_s^{s\bar{s}s}=-0.17\pm{\rm (stat.)}0.15\pm0.03{\rm (syst.)}$ rad.