"Table 576" of "Differential $t\bar{t}$ cross-section measurements using boosted top quarks in the all-hadronic final state with 139 fb$^{-1}$ of ATLAS data"

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 ($p_{\rm T}$) greater than 500 GeV. The observed data are unfolded to remove detector effects. The particle-level cross-section, multiplied by the $t\bar{t}\rightarrow WWb\bar{b}$ branching fraction and measured in a fiducial phase space defined by requiring the leading and second-leading jets to have $p_{\rm T}$ > 500 GeV and $p_{\rm T}$ > 350 GeV, respectively, is $331 \pm 3 \rm{(stat.)} \pm 39 \rm{(syst.)}$ fb. This is approximately 20% lower than the prediction of $398^{+48}_{-49}$ fb by POWHEG+PYTHIA8 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 $1.94 \pm 0.02 \rm{(stat.)} \pm 0.25 \rm{(syst.)}$ pb. This agrees with the NNLO prediction of $1.96^{+0.02}_{-0.17}$ 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.

本文报道了大型强子对撞机（Large Hadron Collider, LHC）上ATLAS探测器（ATLAS）采集的13 TeV质子-质子碰撞中，高横动量顶夸克对产生过程（boosted top-quark pair-production）的单微分、双微分及三微分截面（single-, double-, and triple-differential cross-sections）测量结果。顶夸克通过强子衰变（hadronic decay）被观测到，并被重建为大半径喷注（large-radius jets），其中领头喷注（leading jet）的横向动量（transverse momentum, $p_{
m T}$）大于500 GeV。观测数据经解卷（unfolding）处理以消除探测器效应的影响。在 fiducial相空间（fiducial phase space）内测量的粒子级截面（particle-level cross-section），乘以$tar{t}
ightarrow WWbar{b}$的分支比（branching fraction），且该 fiducial相空间的定义为领头喷注（leading jet）与次领头喷注（second-leading jet）的横向动量分别大于500 GeV和350 GeV，该测量结果为$331 pm 3
m{(stat.)} pm 39
m{(syst.)}$ 飞靶恩（femtobarn, fb）。该结果较采用次领头阶（next-to-leading-order, NLO）精度的POWHEG+PYTHIA8预言的$398^{+48}_{-49}$ fb低约20%，但在理论不确定性（theoretical uncertainties）范围内与该预言相符。本文同时给出部分子级（parton level）的测量结果：通过去除顶夸克衰变、部分子喷注演化（parton showering）及强子化（hadronization）效应，得到可与固定阶次次领头阶（fixed-order next-to-next-to-leading-order, NNLO）计算结果直接比对的结果。在与粒子级 fiducial相空间类似的 fiducial相空间内测量的部分子级截面为$1.94 pm 0.02
m{(stat.)} pm 0.25
m{(syst.)}$ 皮靶恩（picobarn, pb），该结果与$1.96^{+0.02}_{-0.17}$ pb的NNLO预言值一致。多数NLO模型与微分截面结果符合较好，而NNLO计算结果与实验数据的符合程度总体更优。本文采用标准模型有效场论（Standard Model effective field theory, SMEFT）形式对微分截面进行诠释，并对多个四费米子算符（four-fermion operators）的威尔逊系数（Wilson coefficients）设定了约束。