Measurement of jet substructure in boosted $t\bar{t}$ events with the ATLAS detector using 140 fb$^{-1}$ of 13 TeV $pp$ collisions

Measurements of the substructure of top-quark jets are presented using top quarks produced in $pp$ interactions at 13~TeV and recorded with the ATLAS detector. Top-quark jets reconstructed with the anti-$k_t$ algorithm with a radius parameter $R=1.0$ are selected in top-quark pair ($t\bar{t}$) events with one top-quark decaying semileptonically and the other hadronically, and in $t\bar{t}$ events where both top-quarks decay hadronically. The measured top-quark jets are required to have transverse momentum $p_\text{T}$~${>}$~350~GeV and $p_\text{T}$~${>}$~500~GeV in the semileptonic and fully hadronic decay channels, respectively. The one- and two-dimensional differential cross-sections for eight substructure variables, defined using only the charged components of the jets, are measured in a particle-level phase space by correcting for the smearing and acceptance effects induced by the detector. The differential cross-sections are compared to several Monte Carlo (MC) predictions obtained matching top-quark pair production quantum chromodynamic (QCD) predictions at next-to-leading order (NLO) precision in the strong coupling constant $\alpha_\text{S}$ to leading order (LO) parton shower and hadronization generators.