Higgs production in association with off-shell top-antitop pairs at NLO EW and QCD at the LHC

TL;DR

This work delivers the first full NLO electroweak corrections to Higgs production in association with off-shell top–antitop pairs at the LHC, including all interference, off-shell, and non-resonant effects in pp → e^+ ν_e μ^- ν̄_μ b b̄ H. The calculation achieves exact virtual amplitudes up to 9-point functions using Recola and Collier, with cross-checks from two double-pole approximations to assess off-shell contributions. The authors also provide combined predictions with NLO QCD in additive and multiplicative schemes, showing that EW effects are small for integrated cross sections but can be significant in differential distributions, especially at high energy, while QCD corrections dominate. The results offer precise, realistic predictions for experimental analyses, including photon-induced channels and a thorough validation program. Overall, the study advances precision Higgs physics in ttH-like final states by addressing off-shell dynamics and providing robust benchmarks for LHC Run II and beyond.

Abstract

We present NLO electroweak corrections to Higgs production in association with off-shell top-antitop quark pairs. The full process $\text{p}\text{p}\to\text{e}^+ν_{\text{e}} μ^-\barν_μ\text{b}\bar{\text{b}} \text{H}$ is considered, and hence all interference, off-shell, and non-resonant contributions are taken into account. The electroweak corrections turn out to be below one per cent for the integrated cross section but can exceed $10\%$ in certain phase-space regions. In addition to its phenomenological relevance, the computation constitutes a major technical achievement as the full NLO virtual corrections involving up to 9-point functions have been computed exactly. The results of the full computation are supported by two calculations in the double-pole approximation. These also allow to infer the effect of off-shell contributions and emphasise their importance especially for the run II of the LHC. Finally, we present combined predictions featuring both NLO electroweak and QCD corrections in a common set-up that will help the experimental collaborations in their quest of precisely measuring the aforementioned process.

Figures (10)

• Figure 1: Sample tree-level Feynman diagrams with two (left), one (middle) and no (right) top-quark resonances.
• Figure 2: Sample tree-level Feynman diagrams with photons in the initial state.
• Figure 3: Two Feynman diagrams squared for real corrections featuring interference between QCD and EW tree-level diagrams. The decay products of the top quarks are not shown as their inclusion does not alter the discussion.
• Figure 4: Sample one-loop Feynman diagrams squared. On the left-hand side, the diagram represents an EW correction to the QCD process which can also be seen as a QCD correction to the EW amplitude interfered with the QCD amplitude. On the right-hand side, a QCD correction to the QCD amplitude interfered with the EW amplitude is displayed. The decay products of the top quarks are not shown as their inclusion does not alter the discussion.
• Figure 5: Example of nonagon and octagon one-loop Feynman diagrams.