Precise measurement of the <i>tt </i>production cross-section and lepton differential distributions in <i>eμ </i>dilepton events from √<i>s</i> = 13 TeV <i>pp</i> collisions with the ATLAS detector

The inclusive top quark pair (<i>t</i><div style="position: relative; direction: ltr; display: inline-block;"><div style="inset: 0px; opacity: 0.001; overflow: hidden; position: absolute; user-select: none;">t̄</div>t̄</div><i> </i>) cross-section <i>σ</i>_<i>t</i><div style="position: relative; direction: ltr; display: inline-block;"><sub/><div style="inset: 0px; opacity: 0.001; overflow: hidden; position: absolute; user-select: none;">_{_t̄}</div>_{_<i>t̄</i>}</div>_{<i> </i>}has been measured in √<i>s </i>= 13 TeV proton-proton collisions, using 140 fb⁻¹ of data collected by the ATLAS experiment at the Large Hadron Collider. Using events with an opposite-charge <i>eμ </i>pair and <i>b</i>-tagged jets, the cross-section is measured to be:<br/><br/><i>σ</i>_<i>t</i><div style="position: relative; direction: ltr; display: inline-block;"><sub/><div style="inset: 0px; opacity: 0.001; overflow: hidden; position: absolute; user-select: none;">_{_t̄}</div>_{_<i>t̄</i>}</div>_{<i> </i>}= 829.3 ± 1.3 (stat) ± 8.0 (syst) ± 7.3 (lumi) ± 1.9 (beam) pb,<br/><br/>where the uncertainties reflect the limited size of the data sample, experimental and theoretical systematic effects, the integrated luminosity, and the proton beam energy, giving a total uncertainty of 1.3%. The result is used to determine the top quark pole mass via the dependence of the predicted cross-section on <i>m</i>^pole<i>_t</i>, giving <i>m</i>^pole<sub style="font-style: italic;">t</sub> = 172.8^+1.5_−1.7 GeV. The same event sample is used to measure absolute and normalised differential cross-sections for the <i>t</i><div style="position: relative; direction: ltr; display: inline-block;"><div style="inset: 0px; opacity: 0.001; overflow: hidden; position: absolute; user-select: none;">t̄</div>t̄</div><i> </i>→ <i>eμν</i><div style="position: relative; direction: ltr;display: inline-block;"><i/><div style="inset: 0px; opacity: 0.001; overflow: hidden; position: absolute; user-select: none;"><i><i>ν̄nu bar</i></i></div><i><i>̄</i></i></div><i><i>b</i></i><div style="position: relative; direction: ltr;display: inline-block;"><i/><div style="inset: 0px; opacity: 0.001; overflow: hidden; position: absolute; user-select: none;"><i>b̄b bar</i></div><i>̄</i></div><i> process as a function of single-lepton and dilepton kinematic variables. Complementary measurements of </i><div style="position: relative; direction: ltr;display: inline-block;"><i><i>eμb</i></i><div style="inset: 0px; opacity: 0.001; overflow: hidden; position: absolute; user-select: none;"><i>b̄b bar</i></div><i>̄</i></div><i>production, treating both <i>t</i></i><div style="position: relative; direction: ltr; display: inline-block;"><i/><div style="inset: 0px; opacity: 0.001; overflow: hidden; position: absolute; user-select: none;"><i>t̄</i></div><i>t̄</i></div><i><i> </i> and <i>Wt</i> events as signal, are also provided. Both sets of differential cross-sections are compared to the predictions of various Monte Carlo event generators, demonstrating that the state-of-the-art generators Powheg MiNNLO and Powheg <i>bb</i>4<i>l</i> describe the data better than Powheg hvq.</i>