Measurement of the $\mathrm{t}\overline{\mathrm{t}}$ production cross section, the top quark mass, and the strong coupling constant using dilepton events in pp collisions at $\sqrt{s} =$ 13 TeV
A measurement of the top quark–antiquark pair production cross section $\sigma {\mathrm {t}\overline{\mathrm {t}}} $ in proton–proton collisions at a centre-of-mass energy of 13 $,\text {Te}\text {V}$ is presented. The data correspond to an integrated luminosity of $35.9{,\text {fb}^{-1}} $ , recorded by the CMS experiment at the CERN LHC in 2016. Dilepton events ( $\mathrm {e}^{\pm }$ $\mathrm {\mu }^{{\mp }}$ , $\mathrm {\mu ^+}\mathrm {\mu ^-}$ , $\mathrm {e}^+\mathrm {e}^-$ ) are selected and the cross section is measured from a likelihood fit. For a top quark mass parameter in the simulation of $ m\mathrm {\mathrm {t}} ^{\mathrm {MC}} = 172.5 ,\text {Ge}\text {V} $ the fit yields a measured cross section $\sigma {\mathrm {t}\overline{\mathrm {t}}} = 803 \pm 2 ,\text {(stat)} \pm 25 ,\text {(syst)} \pm 20 ,\text {(lumi)} ,\text {pb} $ , in agreement with the expectation from the standard model calculation at next-to-next-to-leading order. A simultaneous fit of the cross section and the top quark mass parameter in the powheg simulation is performed. The measured value of $m\mathrm {\mathrm {t}} ^{\mathrm {MC}} = 172.33 \pm 0.14 ,\text {(stat)} ,^{+0.66-0.72} ,\text {(syst)} ,\text {Ge}\text {V} $ is in good agreement with previous measurements. The resulting cross section is used, together with the theoretical prediction, to determine the top quark mass and to extract a value of the strong coupling constant with different sets of parton distribution functions.
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