Measurement of $\text{t}\overline{\text{t}}$ normalised multi-differential cross sections in $\text{pp}$ collisions at $\sqrt{s}=13\phantom{\rule{0.166667em}{0ex}}\text{TeV}$ , and simultaneous determination of the strong coupling strength, top quark pole mass, and parton distribution functions

Normalised multi-differential cross sections for top quark pair ( $\text{t}\overline{\text{t}}$ ) production are measured in proton-proton collisions at a centre-of-mass energy of 13 $\phantom{\rule{0.166667em}{0ex}}\text{TeV}$ using events containing two oppositely charged leptons. The analysed data were recorded with the CMS detector in 2016 and correspond to an integrated luminosity of $35.9\phantom{\rule{0.166667em}{0ex}}{\text{fb}}^{-1}$ . The double-differential $\text{t}\overline{\text{t}}$ cross section is measured as a function of the kinematic properties of the top quark and of the $\text{t}\overline{\text{t}}$ system at parton level in the full phase space. A triple-differential measurement is performed as a function of the invariant mass and rapidity of the $\text{t}\overline{\text{t}}$ system and the multiplicity of additional jets at particle level. The data are compared to predictions of Monte Carlo event generators that complement next-to-leading-order (NLO) quantum chromodynamics (QCD) calculations with parton showers. Together with a fixed-order NLO QCD calculation, the triple-differential measurement is used to extract values of the strong coupling strength ${\alpha }_{S}$ and the top quark pole mass ( ${m}_{\text{t}}^{\text{pole}}$ ) using several sets of parton distribution functions (PDFs). The measurement of ${m}_{\text{t}}^{\text{pole}}$ exploits the sensitivity of the $\text{t}\overline{\text{t}}$ invariant mass distribution to ${m}_{\text{t}}^{\text{pole}}$ near the production threshold. Furthermore, a simultaneous fit of the PDFs, ${\alpha }_{S}$ , and ${m}_{\text{t}}^{\text{pole}}$ is performed at NLO, demonstrating that the new data have significant impact on the gluon PDF, and at the same time allow an accurate determination of ${\alpha }_{S}$ and ${m}_{\text{t}}^{\text{pole}}$ . The values ${\alpha }_{S}\left({m}_{\text{Z}}\right)=0.1135{}_{-0.0017}^{+0.0021}$ and ${m}_{\text{t}}^{\text{pole}}=170.5±0.8\phantom{\rule{0.166667em}{0ex}}\text{GeV}$ are extracted, which account for experimental and theoretical uncertainties, the latter being estimated from NLO scale variations. Possible effects from Coulomb and soft-gluon resummation near the $\text{t}\overline{\text{t}}$ production threshold are neglected in these parameter extractions. A rough estimate of these effects indicates an expected correction of ${m}_{\text{t}}^{\text{pole}}$ of the order of $+1\phantom{\rule{0.166667em}{0ex}}\text{GeV}$ , which can be regarded as additional theoretical uncertainty in the current ${m}_{\text{t}}^{\text{pole}}$ extraction.