Top-Quark Mediated Effects in Hadronic Higgs-Strahlung

TL;DR

This work identifies and quantifies a previously neglected class of top-quark–mediated contributions to Higgs-Strahlung (VH) production at hadron colliders, which are formally of order $g^3\lambda_t\alpha_s^2$. Real-emission diagrams $R_I$ and $R_{II}$ are computed exactly, while the virtual contributions $V_I$ and $V_{II}$ are evaluated using a heavy-top expansion, with validity checks against full mass dependence. The results indicate percent-level corrections: typically below 1% at the Tevatron and about 1–3% at the LHC, increasing with $M_H$ and energy. The study provides updated VH cross sections and demonstrates that these terms should be included for precision predictions, with plans to incorporate them into vh@nnlo and notes on related effects in weak-boson fusion.

Abstract

Novel contributions to the total inclusive cross section for Higgs-Strahlung in the Standard Model at hadron colliders are evaluated. Although formally of order $α_s^2$, they have not been taken into account in previous NNLO predictions. The terms under consideration are induced by Higgs radiation off top-quark loops and thus proportional to the top-quark Yukawa coupling. At the Tevatron, their effects to HW production are below 1% in the relevant Higgs mass range, while for HZ production, we find corrections between about 1% and 2%. At the LHC, the contribution of the newly evaluated terms to the cross section is typically of the order of 1%-3%. Based on these results, we provide updated predictions for the total inclusive Higgs-Strahlung cross section at the Tevatron and the LHC.

Figures (9)

• Figure 1: (a) Leading order Feynman diagram contributing to the Higgs-Strahlung process; (b) real corrections at .9 NLO .9 QCD; (c) $gg$ component not covered by Drell-Yan-like corrections.
• Figure 2: (a),(b) Diagrams of group $V_\text{I}$ and (c) group $R_\text{I}$ contributing to the process $q \bar{q} \rightarrow V\!H{}(g)$ at order $g^3\lambda_t\alpha_s^2$.
• Figure 3: (a),(b) Diagrams of group $V_\text{II}$ and (c) group $R_\text{II}$ contributing to the process $q \bar{q} \rightarrow Z\!H{}(g)$ at order $g^3\lambda_t\alpha_s^2$.
• Figure 4: Drell-Yan-like diagrams with closed top- and bottom-quark loops.
• Figure 5: Asymptotic expansion of the diagram in Fig. \ref{['fig::vhneu']} (a). The diagrams left of $\otimes$ are evaluated after setting their external momenta to zero. The result determines the expression to be inserted into the effective $\bar{q}qV\!H{}$ or $ggH$ vertex in the diagram right of $\otimes$. For details on the general method, see Refs. Smirnov:1994tgSmirnov:2002pjHarlander:1999cs, for example.