Mixed QCD-electroweak contributions to Higgs-plus-dijet production at the LHC

TL;DR

This work computes the loop-induced interference between gluon-fusion and weak-boson-fusion Higgs production with two accompanying jets at the LHC, at order $\mathcal{O}(\alpha^2 \alpha_s^3)$. It extends previous studies by including a neglected class of real-emission diagrams and by implementing a fully flexible parton-level Monte Carlo in the vbfnlo framework to explore cross sections and distributions under realistic WBF cuts. The analysis shows that, although the interference has kinematic shapes distinct from pure WBF, its total impact is negligible due to cancellations among quark-flavor channels and the small cross section. The work also provides a numerically stable, cross-checked methodology using two independent tensor-reduction schemes and phase-space slicing techniques, yielding a robust tool for assessing potential contamination of the WBF Higgs signal by GF–WBF interference.

Abstract

We present a calculation of interference effects in Hjj production via gluon fusion and via vector boson fusion, respectively, beyond tree level. We reproduce results recently discussed in the literature, but go beyond this calculation by including a class of diagrams not considered previously. Special care is taken in developing a numerically stable and flexible parton level Monte-Carlo program which allows us to study cross sections and kinematic distributions within experimentally relevant selection cuts. Loop-induced interference contributions are found to exhibit kinematical distributions different in shape from vector boson fusion. Due to the small interference cross section and cancelation among different quark flavor contributions their impact on the signal process is found to be negligible in all regions of phase space, however.

Figures (14)

• Figure 1: Feynman diagram for the tree level process $qq'\hbox{$\rightarrow$} qq'H$ via WBF.
• Figure 2: Feynman diagrams for the tree level process $qq'\hbox{$\rightarrow$} qq'H$ via GF, mediated (a) by a top-quark loop and (b) by the effective $Hgg$ vertex of Eq. (\ref{['eq:hgg-eff']}).
• Figure 3: Representative loop contribution to the interference cross section for $qq'\hbox{$\rightarrow$} qq'H$ via WBF and GF, respectively, at order $\mathcal{O}(\alpha^2 \alpha_s^3)$, where the 1-loop WBF amplitude interferes with the tree-level GF amplitude.
• Figure 4: Representative loop contribution to the interference cross section for $qq'\hbox{$\rightarrow$} qq'H$ via WBF and GF, respectively, at order $\mathcal{O}(\alpha^2 \alpha_s^3)$, where the 1-loop GF amplitude interferes with the tree-level WBF amplitude.
• Figure 5: Representative cut amplitudes for the $qq'\hbox{$\rightarrow$} qq'gH$ process via the interference of WBF and GF amplitudes, at order $\mathcal{O}(\alpha^2 \alpha_s^3)$.