Flavour tagged time dependent angular analysis of the \(B_s^{0} \rightarrow J/\psi \phi\) decay and extraction of \(\Delta\Gamma_s\) and the weak phase \(\phi_s\) in ATLAS

Abstract

A measurement of the \(B_s ^{0}\rightarrow J/\psi \phi\) decay parameters, updated to include flavour tagging is reported using \(4.9 fb^{-1}\) of integrated luminosity collected by the ATLAS detector from \(\sqrt{s}= 7\)TeV \(pp\) collisions recorded in 2011 at the LHC. The values measured for the physical parameters are: \begin{eqnarray*} \phi_s & = & 0.12 \pm 0.25(stat.)\pm 0.05(syst.)rad \\ \Delta\Gamma_s & = & 0.053 \pm 0.021(stat.) 0.010(syst.)ps^{-1} \\ \Gamma_s & = & 0.677 \pm 0.007 (stat.)\pm 0.004 (syst.)ps^{-1}\\ |A_{\parallel}(0)|^2 & = & 0.220 \pm 0.008 (stat.)\pm 0.009(syst.)\\ |A_{0}(0)|^2 & = & 0.529 \pm 0.006 (stat.)\pm 0.012(syst.)\\ \delta_\perp & = & 3.89 \pm 0.47(stat.) \pm 0.11(syst.)rad \end{eqnarray*} where the parameter \(\Delta\Gamma_s\) is constrained to be positive. The \(S\)-wave contribution was measured and found to be compatible with zero. Results for \(\phi_s\) and \(\Delta\Gamma_s\) are also presented as \(68\%\) and \(95\%\) likelihood contours, which show agreement with the Standard Model expectations.