Precise measurement of the $t\bar{t}$ production cross-section and lepton differential distributions in $eμ$ dilepton events

TL;DR

The paper addresses the precise measurement of $t\overline{t}$ production cross-sections and lepton differential distributions in $pp$ collisions at $\sqrt{s}=13$ TeV. It employs the full Run 2 ATLAS dataset and analyzes the $t\overline{t} \to W^{+}bW^{-}\bar{b} \to e^{+}\mu^{-}\nu\bar{\nu}b\bar{b}$ channel, plus complementary $e\mu b\bar{b}$ final states, using a double-tagging method and state-of-the-art event generation with Powheg MiNNLO to extract $m_t^{\mathrm{pole}}$ from the cross-section. The results include a precise measurement of $\sigma_{t\overline{t}}$ and a pole-mass determination, along with ten single-differential and three double-differential lepton-distribution cross-sections that test QCD and improve modeling of top-quark production. These measurements constrain perturbative QCD at high scales and provide inputs to refine collider phenomenology and SM tests.

Abstract

Measurements of the inclusive and differential top-quark pair ($t\bar{t}$) cross-sections in proton--proton collisions at $\sqrt{s} = 13$ TeV, using 140 fb$^{-1}$ of data collected by the ATLAS experiment at the Large Hadron Collider, are presented. Events with an opposite-charge $eμ$ pair and $b$-tagged jets are selected, and the inclusive cross-section measurement is used to determine the top-quark pole mass via the dependence of the predicted cross-section on $m_t^\mathrm{pole}$. Complementary measurements of $eμb\bar{b}$ production, treating both $t\bar{t}$ and $tW$ events as signal, are also provided.

Figures (2)

• Figure 1: (a) Distributions of the number of $b$-tagged jets in selected opposite-charge $e\mu$ events. (b) The red line shows the predicted inclusive $t\bar{t}$ cross-section as a function of $m_t^{\mathrm{pole}}$ for the NNPDF3.1_notop PDF set, with the cyan band indicating the total uncertainty in the prediction from PDF+$\alpha_s$ and QCD scale uncertainties. The black points show the experimental measurement with its uncertainty and dependence on the assumed value of $m_t$ through acceptance and background corrections. The dotted line shows the experimental central value at a fixed top quark mass of 172.5 GeV TOPQ-2024-12.
• Figure 2: Differential cross-sections as functions of (a) $p_\mathrm{T}$ and (b) $\eta$ of the leading lepton. The upper panels show the measured absolute $t\bar{t}$ (filled points) and $e\mu b\bar{b}$ (open points) cross-sections with the total uncertainties shown by the shaded bands. The other panels show ratios of various predictions to the measured normalised differential cross-sections. The markers showing the ratios for each prediction and the total uncertainty in the prediction is shown by the error bar. The data statistical uncertainty is shown by the black error bars and the total uncertainty by the cyan or orange band TOPQ-2024-12.