Measurements of t t ̄ differential cross-sections of highly boosted top quarks decaying to all-hadronic final states in pp collisions at √s = 13 TeV using the ATLAS detector

Abstract

Measurements are made of differential cross-sections of highly boosted pair-produced top quarks as a function of top-quark and tt ̄ system kinematic observables using proton–proton collisions at a center-of-mass energy of √s = 13 TeV. The data set corresponds to an in- tegrated luminosity of 36.1 fb−1, recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. Events with two large-radius jets in the final state, one with transverse momentum pT > 500 GeV and a second with pT > 350 GeV, are used for the measurement. The top-quark candidates are separated from the multijet background us- ing jet substructure information and association with a b-tagged jet. The measured spectra are corrected for detector effects to a particle-level fiducial phase space and a parton-level limited phase space, and are compared to several Monte Carlo simulations by means of cal- culated χ2 values. The cross-section for tt ̄ production in the fiducial phase-space region is 292 ± 7 (stat) ± 76(syst) fb, to be compared to the theoretical prediction of 384 ± 36 fb.