First experimental investigation of the running of the top quark mass

Abstract

The first experimental investigation of the running of the top quark mass is presented. The running, defined in the modified minimal subtraction ($\mathrm{\overline{MS}}$) renormalization scheme, is extracted from a measurement of the differential top quark-antiquark ($\mathrm{t\bar{t}}$) production cross section as a function of the invariant mass of the $\mathrm{t\bar{t}}$ system using theoretical predictions at next-to-leading order. The measurement is performed using proton-proton collisions at a centre-of-mass energy of $13~\mathrm{TeV}$ recorded by the CMS detector at the CERN LHC in 2016, corresponding to an integrated luminosity of $35.9~\mathrm{fb^{-1}}$. Candidate $\mathrm{t\bar{t}}$ events are selected in the final state with an electron and a muon of opposite charge, and the differential cross section is determined at the parton level by means of a maximum-likelihood fit to multidifferential distributions. The extracted running is found to be compatible with the solution of the corresponding renormalization group equation, up to a scale on the order of $1~\mathrm{TeV}$