Measurement of the dineutrino system kinematic variables in dileptonic top quark pair production in proton-proton collisions at$\sqrt{s}$ = 13 TeV

Abstract: Differential top quark pair production cross sections are measured in the dilepton final states $\mathrm{e}^{+}\mathrm{e}^{-}$, $\mu^{+}\mu^{-}$, and $\mathrm{e}^{\pm}\mu^{\mp}$, as a function of kinematic variables of the system of two neutrinos: the transverse momentum $p_{\text{T}}^{\nu\nu}$ of the dineutrino system, the minimum distance in azimuthal angle between $\vec{p}_{\text{T}}^{\nu\nu}$ and leptons, and in two dimensions in bins of both observables. The measurements are performed using CERN LHC proton-proton collisions at $\sqrt{s} = 13\,$TeV, recorded by the CMS detector between 2016 and 2018, corresponding to an integrated luminosity of 138 fb$^{-1}$. The measured cross sections are unfolded to the particle level using an unregularized least squares method. The obtained results are found to be in agreement with the latest theory predictions and Monte Carlo simulations.