Measurement of the CP-violating phase $\phi_s$ in $\overline{B}^0_s\rightarrow J/\psi \pi^+\pi^-$ decays

TL;DR

This paper measures the CP-violating phase  in  decays using LHCb data, employing a time-dependent analysis, and finds results consistent with the Standard Model.

Contribution

First measurement of  in  decays using a time-dependent amplitude analysis with direct CP violation consideration.

Findings

 phase measured as 70 b1 68 b1 8 mrad

Result consistent with Standard Model predictions

Analysis used 3 fbb7b1 data from LHCb at 7 and 8 TeV

Abstract

The mixing-induced CP-violating phase $\phi_s$ in ${B}^0_s$ and $\overline{B}^0_s$ decays is measured using the $J/\psi \pi^+\pi^-$ final state in data, taken from 3\,fb$^{-1}$ of integrated luminosity, collected with the LHCb detector in 7 and 8 TeV centre-of-mass $pp$ collisions at the LHC. A time-dependent flavour-tagged amplitude analysis, allowing for direct \CP violation, yields a value for the phase $\phi_s=70\pm 68\pm 8$\,mrad. This result is consistent with the Standard Model expectation and previous measurements.