Measurement of the jet mass distribution and top quark mass in hadronic decays of boosted top quarks in proton-proton collisions at $\sqrt{s}$ = 13 TeV

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 400 GeV. The data
were collected with the CMS detector at the LHC in protonproton collisions and correspond to an integrated luminosity
of 138 fb−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 ± 0.84 GeV.