Higgs Boson Production in Weak Boson Fusion at Next-to-Leading Order

TL;DR

This paper assesses the feasibility of extracting the Higgs coupling to weak bosons from Higgs plus two jets produced via weak-boson fusion at the LHC. It computes the WBF signal at NLO QCD and uses LO matrix elements for the irreducible H+2 jet background, exploring various WBF-defining cuts to optimize signal purity. The authors introduce a simple one-jet rapidity cut as a practical WBF definition, quantify resulting purities, and derive how δg/g scales with purity and experimental uncertainties, projecting ~10% accuracy with ~200 fb^-1 under plausible assumptions. They further compare alternative cuts and provide two estimates of NLO background corrections, both highlighting substantial theoretical uncertainties and the need for a fully differential NLO background calculation to robustly determine the coupling precision and its experimental viability.

Abstract

The weak boson fusion process for neutral Higgs boson production is investigated with particular attention to the accuracy with which the Higgs boson coupling to weak bosons can be determined at CERN Large Hadron Collider (LHC) energies in final states that contain a Higgs boson plus at least two jets. Using fully differential perturbative matrix elements for the weak boson fusion signal process and for the QCD background processes, we generate events in which a Higgs boson is produced along with two jets that carry large transverse momentum. The effectiveness of different prescriptions to enhance the signal to background ratio is studied, and the expected signal purities are calculated in each case. We find that a simple cut on the rapidity of one final-state jet works well. We determine that an accuracy of delta_g/g ~ 10% on the effective coupling g may be possible after ~ 200 fb^-1 of integrated luminosity is accumulated at the LHC.

Figures (17)

• Figure 1: Representative diagrams for the production of a Higgs boson via weak boson fusion: (a) at lowest order; (b),(c) at NLO. Further diagrams can be obtained by crossing incoming and outgoing lines in all cases. All of the virtual corrections are of the vertex correction form, as shown in (b). There are two types of real corrections depicted in (c). The first set corresponds to the emission of a gluon in all possible positions on the quark lines (left-hand diagram) and the second set corresponds to the crossing where a gluon is present in the initial state (right-hand side).
• Figure 2: Representative diagrams for the production of a Higgs boson and two jets at lowest order, calculated in the heavy top-quark limit of the $Hgg$ effective coupling.
• Figure 3: Dependence of the tagging jet pseudo-rapidities on the minimum jet $p_T$ used, for the two cases $m_H=115$ GeV (left) and $m_H=200$ GeV (right). Each of the two tagging jets in the event is entered in these plots, with weight one-half, and the rates assume an integrated luminosity of $1~{\rm fb}^{-1}$. The signal (solid) is calculated at NLO and the background (dashed) at LO. We show results for three different selections of the minimum jet transverse momentum, $p_T > 20$, $40$, and $80$ GeV.
• Figure 4: Numbers of events for the WBF signal and the QCD background as a function of the minimum jet $p_T$, for an integrated luminosity of $1~{\rm fb}^{-1}$. No branching ratios for the Higgs boson decay have been applied. The pseudo-rapidity restriction on one of the jets has been enforced, as in Table \ref{['tab:rates_rapsep']}. The solid line is the NLO signal and the dashed is the LO background.
• Figure 5: Dependence of the tagging jet pseudo-rapidities for jet $p_T > 40$ GeV, for the two cases $m_H=115$ GeV (left) and $m_H=200$ GeV (right). For the background, we show the full result with all contributions included and, for comparison of shapes, the background obtained if only the $qq$, $q \bar{q}$, and $\bar{q} \bar{q}$ initial state contributions are used. The magnitude of the separate component is multiplied by $20$.