Measurement of CP violation in $B_s^0 \to \phi \phi$ decays

TL;DR

This paper reports a measurement of CP violation in $B_s^0 o $ decays using LHCb data, finding results consistent with CP conservation and providing the most precise phase measurement to date.

Contribution

First measurement of CP-violating phase and triple-product asymmetries in $B_s^0 o $ decays with 3.0 fb$^{-1}$ of data, improving precision and testing the Standard Model.

Findings

CP-violating phase ${_s = -0.17 ext{ rad}}$ with uncertainties

Triple-product asymmetries ${A_U}$ and ${A_V}$ consistent with zero

Results align with CP conservation hypothesis

Abstract

A measurement of the decay time dependent CP-violating asymmetry in $B_s^0 \to \phi\phi$ decays is presented, along with measurements of the $T$-odd triple-product asymmetries. In this decay channel, the CP-violating weak phase arises from the interference between $B_s^0$-$\bar{B}_s^0$ mixing and the loop-induced decay amplitude. Using a sample of proton-proton collision data corresponding to an integrated luminosity of $3.0\, fb^{-1}$ collected with the LHCb detector, a signal yield of approximately 4000 $B_s^0 \to \phi\phi$ decays is obtained. The CP-violating phase is measured to be ${\phi_s =-0.17\pm0.15\mathrm{\,(stat)}\pm0.03\mathrm{\,(syst)}}$ rad. The triple-product asymmetries are measured to be ${A_U=-0.003\pm0.017\mathrm{\,(stat)}\pm0.006\mathrm{\,(syst)}}$ and ${A_V=-0.017\pm0.017\mathrm{\,(stat)}\pm0.006\mathrm{\,(syst)}}$. Results are consistent with the hypothesis of CP conservation.