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Measurement of the CP-violating phase ${\varphi }_{s}$ in ${B}_{s}^{0}\to J/\psi \varphi $ decays in ATLAS at 13 TeV

2021    CERN İşbirliği

A measurement of the ${B}_{s}^{0}\to J/\psi \varphi $ decay parameters using $80.5\phantom{\rule{0.166667em}{0ex}}{\mathrm{fb}}^{-1}$ of integrated luminosity collected with the ATLAS detector from 13 $\text{Te}\phantom{\rule{0.333333em}{0ex}}$ proton–proton collisions at the LHC is presented. The measured parameters include the CP-violating phase ${\varphi }_{s}$ , the width difference $\Delta {\Gamma }_{s}$ between the ${B}_{s}^{0}$ meson mass eigenstates and the average decay width ${\Gamma }_{s}$ . The values measured for the physical parameters are combined with those from $19.2\phantom{\rule{0.166667em}{0ex}}{\mathrm{fb}}^{-1}$ of 7 and 8 $\text{Te}\phantom{\rule{0.333333em}{0ex}}$ data, leading to the following: $\begin{array}{cc}{\varphi }_{s}=& -0.087±0.036\phantom{\rule{3.33333pt}{0ex}}\left(\mathrm{stat}.\right)±0.021\phantom{\rule{3.33333pt}{0ex}}\left(\mathrm{syst}.\right)\phantom{\rule{3.33333pt}{0ex}}\mathrm{rad}\\ \Delta {\Gamma }_{s}=& 0.0657±0.0043\phantom{\rule{3.33333pt}{0ex}}\left(\mathrm{stat}.\right)±0.0037\phantom{\rule{3.33333pt}{0ex}}{\left(\mathrm{syst}.\right)\phantom{\rule{3.33333pt}{0ex}}\mathrm{ps}}^{-1}\\ {\Gamma }_{s}=& 0.6703±0.0014\phantom{\rule{3.33333pt}{0ex}}\left(\mathrm{stat}.\right)±0.0018\phantom{\rule{3.33333pt}{0ex}}{\left(\mathrm{syst}.\right)\phantom{\rule{3.33333pt}{0ex}}\mathrm{ps}}^{-1}\end{array}$ Results for ${\varphi }_{s}$ and $\Delta {\Gamma }_{s}$ are also presented as 68% confidence level contours in the ${\varphi }_{s}$ – $\Delta {\Gamma }_{s}$ plane. Furthermore the transversity amplitudes and corresponding strong phases are measured. ${\varphi }_{s}$ and $\Delta {\Gamma }_{s}$ measurements are in agreement with the Standard Model predictions.