A bstract Measurements of single-, double-, and triple-differential cross-sections are presented for boosted top-quark pair-production in 13 TeV proton–proton collisions recorded by the ATLAS detector at the LHC. The top quarks are observed through their hadronic decay and reconstructed as large-radius jets with the leading jet having transverse momentum ( p T ) greater than 500 GeV. The observed data are unfolded to remove detector effects. The particle-level cross-section, multiplied by the tt̄→ WWbb̄ t t ¯ → WWb b ¯ branching fraction and measured in a fiducial phase space defined by requiring the leading and second-leading jets to have p T > 500 GeV and p T > 350 GeV, respectively, is 331 ± 3(stat.) ± 39(syst.) fb. This is approximately 20% lower than the prediction of 398₋₄₉⁺⁴⁸ 398 − 49 + 48 fb by P owheg +P ythia 8 with next-to-leading-order (NLO) accuracy but consistent within the theoretical uncertainties. Results are also presented at the parton level, where the effects of top-quark decay, parton showering, and hadronization are removed such that they can be compared with fixed-order next-to-next-to-leading-order (NNLO) calculations. The parton-level cross-section, measured in a fiducial phase space similar to that at particle level, is 1 . 94 ± 0 . 02(stat.) ± 0 . 25(syst.) pb. This agrees with the NNLO prediction of 1.96-0.17+0.02 1.96 − 0.17 + 0.02 pb. Reasonable agreement with the differential cross-sections is found for most NLO models, while the NNLO calculations are generally in better agreement with the data. The differential cross-sections are interpreted using a Standard Model effective field-theory formalism and limits are set on Wilson coefficients of several four-fermion operators.
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Aad et al. (2023) studied this question.