Intermediate-Mass Higgs Searches in Weak Boson Fusion

TL;DR

This work analyzes intermediate-mass Higgs searches at the LHC via weak-boson fusion across three decay channels: H→γγ, H→WW, and H→ττ. It develops a parton-level framework with forward-jet tagging and a central minijet veto, leveraging distinct color-flow patterns to suppress QCD backgrounds and achieve strong signal-to-background ratios. The study shows that H→γγ can reach 5σ for 110–150 GeV with ~40–50 fb⁻¹, H→WW can yield a very clean, low-luminosity discovery over 130–200 GeV, and H→ττ enables direct measurement of Higgs-fermion couplings with tens of fb⁻¹, together offering a robust, multi-channel discovery and coupling-physics program. The results highlight the complementary role of WBF channels to inclusive gluon-fusion searches and outline the practical considerations for minijet-veto calibrations via Zjj/Wjj processes, with implications for MSSM Higgs scenarios as well.

Abstract

Weak boson fusion is a copious source of intermediate mass Higgs bosons at the LHC. The additional very energetic forward jets in these events are powerful background suppression tools. I analyze the decays H -> gamma gamma and H -> W^(*)W^(*) -> e mu pTmiss, with the latter a potential discovery channel, and the decay H -> tau tau -> lep had pTmiss as a method for achieving the first direct measurement of a Higgs-fermion coupling. I perform parton level analyses of the signal and dominant backgrounds for each decay mode, and demonstrate kinematic cuts and other important tools neccessary to achieve an S/B > 1/1 rate in all cases. I also perform cross section calculations with additional gluon emission which provide an estimate of a minijet veto probability. I show that a 5 sigma H -> gamma gamma observation can be made for 110 GeV < M_H < 150 GeV with modest luminosity, order 40-50 fb^-1, overlapping the region explored by the CERN LEP and Fermilab Tevatron. For 130 GeV < M_H < 200 GeV, I show that H -> WW can achieve a 5 sigma observation with S/B much greater than 1/1 with extremely low luminosity, about 2-10 fb^-1 over almost the entire range. This is the most promising search channel in the 130-200 GeV mass range. It overlaps the H -> gamma gamma region and nicely complements the H -> WW measurement that can be made with very low luminosity in inclusive gg -> H production. I further show that a Higgs-fermion coupling can be directly measured via the H -> tau tau decay with only about 60 fb^-1.

Figures (24)

• Figure 1: Weak boson fusion Higgs production.
• Figure 2: Normalized minimum and maximum $p_T$ distributions of the two jets in signal $qq\to qqH,H\to\gamma\gamma$ events at the LHC, with $M_H = 120$ GeV. No cuts are imposed; the vertical dashed lines represent the minimum detector acceptance $p_{T_j}$ cut of Eq. \ref{['eq:basic']}.
• Figure 3: Normalized pseudo-rapidity distributions of (a) the most central and (b) the most forward of the two tagging jets in $\gamma\gamma jj$ events at the LHC. The generic acceptance cuts of Eq. (\ref{['eq:basic']}) are imposed. Results are shown for the $qq\to qqH$ signal at $m_H=120$ GeV (solid line) and for the irreducible QCD $\gamma\gamma jj$ background (dashed line).
• Figure 4: Normalized pseudo-rapidity distributions of the most forward of the two photons in $\gamma\gamma jj$ events at the LHC. The generic acceptance cuts of Eq. (\ref{['eq:basic']}) are imposed. Results are shown for the $qq\to qqH$ signal at $m_H=120$ GeV (solid line) and for the irreducible QCD $\gamma\gamma jj$ background (dashed line).
• Figure 5: Normalized pseudo-rapidity distributions of both photon rapidities with respect to the center of the tagging jets (as discussed in the text) in $\gamma\gamma jj$ events at the LHC. The acceptance cuts of Eq. (\ref{['eq:basic']}) are imposed. Results are shown for the $qq\to qqH$ signal at $m_H=120$ GeV (solid line) and for the irreducible QCD $\gamma\gamma jj$ background (dashed line).