NLO QCD corrections to off-shell top-antitop production with leptonic decays in association with a Higgs boson at the LHC

TL;DR

This work delivers a full NLO QCD calculation for hadronic ttH production with leptonic top decays, including off-shell, non-resonant, and interference effects. Using Recola and Collier within a Catani–Seymour subtraction framework, the authors compare fixed and dynamical factorization/renormalization scales at 13 TeV and provide integrated as well as differential predictions. They find a robust K-factor around 1.17 and significantly improved perturbative stability when employing a dynamical scale, while finite-top-width effects remain below 1%. The study validates the computational setup through extensive cross-checks with independent tools and related processes, highlighting the methodological strength of the Recola/Collier pipeline for complex NLO calculations.

Abstract

We compute the hadronic production of top-antitop pairs in association with a Higgs boson at next-to-leading-order QCD, including the decay of the top and antitop quark into bottom quarks and leptons. Our computation is based on full leading and next-to-leading-order matrix elements for $e^+ ν_e μ^-\barν_μb \bar{b} H(j)$ and includes all non-resonant contributions, off-shell effects and interferences. Numerical results for the integrated cross section and several differential distributions are given for the LHC operating at 13 TeV using a fixed and a dynamical factorization and renormalization scale. The use of the dynamical instead of the fixed scale improves the perturbative stability in high-energy tails of most distributions, while the integrated cross section is hardly affected differing by only about one per cent and leading to the same K factor of 1.17.

Figures (8)

• Figure 1: Representative tree-level Feynman diagrams with \ref{['fig:born_2tops_gg_tchannel']}--\ref{['fig:born_2tops_uxu_schannel']} two (top), \ref{['fig:born_1top_uxu_schannel']}--\ref{['fig:born_1top_gg_tchannel']} one (middle) and \ref{['fig:born_notops_gg_tchannel_z0']}--\ref{['fig:born_notops_uxu_tchannel']} no top-quark resonances (bottom).
• Figure 2: Representative hexagon and heptagon one-loop Feynman diagrams with two top-quark resonances.
• Figure 3: Scale dependence of the LO and NLO integrated cross section at the $13\,\text{TeV}\xspace$ LHC. The renormalization and factorization scales are varied around the central values of the fixed ($\mu_0=\mu_\text{fix}$, dash-dotted lines) and dynamical scale ($\mu_0=\mu_\text{dyn}$, solid lines). For the dynamical scale the variation with $\mu_\text{R}$ while keeping $\mu_\text{F}=\mu_\text{dyn}$ fixed and vice versa is shown with dashed lines.
• Figure 4: Zero-top-width extrapolation of the LO and NLO cross section at the LHC at $\sqrt{s}=13\,\text{TeV}\xspace$ for fixed scale $\mu_0=\mu_\text{fix}$.
• Figure 5: Transverse-momentum distributions at the LHC at $\sqrt{s}=13\,\text{TeV}\xspace$ for fixed scale $\mu_0=\mu_\text{fix}$: \ref{['plot:transverse_momentum_positron_fix']} for the positron (left) and \ref{['plot:transverse_momentum_b1_fix']} for the harder $\text{b}$ jet (right). The lower panels show the $K$ factor.