$t\bar{t}b\bar{b}$ at the LHC: On the size of corrections and $b$-jet definitions

TL;DR

This paper presents a detailed NLO QCD calculation for $t\bar{t}b\bar{b}$ production at the 13 TeV LHC, including all relevant diagrams and effects, to improve theoretical predictions for top-quark and Higgs measurements.

Contribution

It provides the first comprehensive NLO QCD analysis of $t\bar{t}b\bar{b}$ production including off-shell effects, interferences, and bottom-quark PDF contributions.

Findings

Results show significant scale and PDF uncertainties.

Impact of bottom-quark PDFs on cross sections is quantified.

Differential distributions are provided for experimental comparisons.

Abstract

We report on the calculation of the next-to-leading order QCD corrections to the production of a $t\bar{t}$ pair in association with two heavy-flavour jets. We concentrate on the di-lepton $t\bar{t}$ decay channel at the LHC with $\sqrt{s}=13$ TeV. The computation is based on $pp \to e^+ \nu_e\, \mu^-\bar{\nu}_\mu\, b\bar{b} \,b\bar{b}$ matrix elements and includes all resonant and non-resonant diagrams, interferences and off-shell effects of the top quark and the $W$ gauge boson. As it is customary for such studies, results are presented in the form of inclusive and differential fiducial cross sections. We extensively investigate the dependence of our results upon variation of renormalisation and factorisation scales and parton distribution functions in the quest for an accurate estimate of the theoretical uncertainties. We additionally study the impact of the contributions induced by the bottom-quark parton density. Results presented here are particularly relevant for measurements of $t\bar{t}H(H\to b\bar{b})$ and the determination of the Higgs coupling to the top quark. In addition, they might be used for precise measurements of the top-quark fiducial cross sections and to investigate top-quark decay modelling at the LHC.