Measurement of the differential tt¯ production cross section as a function of the jet mass and extraction of the top quark mass in hadronic decays of boosted top quarks

Eur Phys J C Part Fields. 2023;83(7):560. doi: 10.1140/epjc/s10052-023-11587-8. Epub 2023 Jul 3.

Abstract

A measurement of the jet mass distribution in hadronic decays of Lorentz-boosted top quarks is presented. The measurement is performed in the lepton + jets channel of top quark pair production (tt¯) events, where the lepton is an electron or muon. The products of the hadronic top quark decay are reconstructed using a single large-radius jet with transverse momentum greater than 400GeV. The data were collected with the CMS detector at the LHC in proton-proton collisions and correspond to an integrated luminosity of 138fb-1. The differential tt¯ production cross section as a function of the jet mass is unfolded to the particle level and is used to extract the top quark mass. The jet mass scale is calibrated using the hadronic W boson decay within the large-radius jet. The uncertainties in the modelling of the final state radiation are reduced by studying angular correlations in the jet substructure. These developments lead to a significant increase in precision, and a top quark mass of 173.06±0.84GeV.