Measurement of the flavour-specific CP-violating asymmetry $a_{\rm sl}^s$ in $B_s^0$ decays

TL;DR

This paper measures the flavour-specific CP-violating asymmetry in Bs meson decays using LHC data, finding results consistent with the Standard Model within uncertainties.

Contribution

First measurement of a_{sl}^s in pp collisions at 7 TeV using semileptonic Bs decays with data-driven efficiency corrections.

Findings

Measured a_{sl}^s = (-0.06 +/- 0.50 +/- 0.36)%

Results are consistent with Standard Model predictions

Demonstrated data-driven methods for efficiency ratio measurement

Abstract

The CP-violating asymmetry a_{sl}^s is studied using semileptonic decays of Bs and anti-Bs mesons produced in pp collisions at a centre-of-mass energy of 7 TeV at the LHC, exploiting a data sample corresponding to an integrated luminosity of 1.0/fb. The reconstructed final states are Ds^(+/-)\mu ^(-/+), with the Ds^(+/-) particle decaying in the \phi\pi^(+/-) mode. The Ds^(+/-)\mu ^{-/+) yields are summed over Bs and anti-Bs initial states, and integrated with respect to decay time. Data-driven methods are used to measure efficiency ratios. We obtain $a_{sl}^s$ = (-0.06 +/- 0.50 +/- 0.36)%, where the first uncertainty is statistical and the second systematic.