First measurement of the CP-violating phase in $B_s^0 \to \phi \phi$ decays

TL;DR

This paper reports the first measurement of the CP-violating phase in $B_s^0 o \,phi\phi$ decays, using LHCb data, providing insights into CP violation in the quark sector and testing Standard Model predictions.

Contribution

It presents the first flavor-tagged, time-dependent measurement of the CP-violating phase in $B_s^0 \to \phi\phi$ decays, using 1.0 fb$^{-1}$ of LHCb data.

Findings

Measured CP-violating phase interval: [-2.46, -0.76] rad at 68% CL.

P-value of Standard Model prediction: 16%.

Obtained 880 $B_s^0 \to \phi\phi$ signal decays.

Abstract

A first flavour-tagged measurement of the time-dependent CP-violating asymmetry in $B_s^0 \to \phi\phi$ decays is presented. In this decay channel, the CP-violating weak phase arises due to CP violation in the interference between $B_s^0$-$\bar{B}_s^0$ mixing and the $b \to s \bar{s} s $ gluonic penguin decay amplitude. Using a sample of $pp$ collision data corresponding to an integrated luminosity of $1.0\; fb^{-1}$ and collected at a centre-of-mass energy of $7 \rm TeV$ with the LHCb detector, $880\ \B_s^0 \to \phi\phi$ signal decays are obtained. The CP-violating phase is measured to be in the interval [-2.46, -0.76] \rm rad$ at 68% confidence level. The p-value of the Standard Model prediction is 16%.