Measurement of the CP-violating phase \(\phi_s\) and the \(B^0_s\) meson decay width difference with \(B^0_s \to J/\psi\phi\) decays in ATLAS

Abstract

A measurement of the \(B^0_s\) decay parameters in the \(B^0_s \to J/\psi\phi\) channel using an integrated luminosity of 14.3 \(\mathrm{fb}^{-1}\) collected by the ATLAS detector from 8 TeV \(pp\) collisions at the LHC is presented. The measured parameters include the \(CP\)-violating phase \(\phi_s\), the decay width \(\Gamma_s\) and the width difference between the mass eigenstates \(\Delta\Gamma_s\). The values measured for the physical parameters are statistically combined with those from 4.9 \(\mathrm{fb}^{-1}\) of 7 TeV data, leading to the following: \begin{eqnarray*} \phi_s & = & -0.090 \pm 0.078\;\mathrm{(stat.)} \pm 0.041\;\mathrm{(syst.)\;rad} \\ \Delta\Gamma_s & = & 0.085 \pm 0.011\;\mathrm{(stat.)} \pm 0.007\;\mathrm{(syst.)\;ps}^{-1} \\ \Gamma_s & = & 0.675 \pm 0.003\;\mathrm{(stat.)} \pm 0.003\;\mathrm{(syst.)\;ps}^{-1}. \end{eqnarray*} In the analysis the parameter \(\Delta\Gamma_s\) is constrained to be positive. Results for \(\phi_s\) and \(\Delta\Gamma_s\) are also presented as 68% and 95% likelihood contours in the \(\phi_s-\Delta\Gamma_s\) plane. Also measured in this decay channel are the transversity amplitudes and corresponding strong phases. All measurements are in agreement with the Standard Model predictions.