[Paper Review] Higgs production plus two jets at hadron colliders

V. Del Duca, William B. Kilgore+3 more|ArXiv.org|Sep 17, 2001

Particle physics theoretical and experimental studies3 citations

TL;DR

This paper presents a next-to-leading-order calculation of Higgs boson production in association with two jets via gluon fusion, including full top-quark mass dependence, and compares it to the large-top-mass limit. It finds the large-top-mass approximation remains accurate for Higgs masses below 200 GeV and jet transverse momenta below the top mass, while jet angular correlations—particularly rapidity separation and azimuthal decorrelation—effectively distinguish gluon-fusion from weak-boson fusion processes at the LHC.

ABSTRACT

In this talk we present a calculation of Higgs production via gluon fusion in association with two jets, including the full top-quark mass dependence, and compare it to the large top-mass limit. We find that the large top-mass limit is a good approximation as long as the Higgs mass is smaller than the top quark pair mass, and the jet transverse energies are smaller than the top mass. In addition, we compare Higgs production via gluon fusion and via weak-boson fusion, and consider final-state distributions, like the rapidity interval between the jets and the jet-jet azimuthal decorrelation, which may allow us to distinguish one fusion process from the other.

Motivation & Objective

• To evaluate the validity of the large-top-quark mass approximation in Higgs + 2 jet production via gluon fusion at hadron colliders.
• To compare the contributions of gluon fusion and weak-boson fusion to Higgs + 2 jet final states at the LHC.
• To identify kinematic observables—such as rapidity separation and azimuthal decorrelation—that can distinguish between gluon-fusion and weak-boson fusion mechanisms.
• To assess the impact of jet transverse momentum and dijet invariant mass on the reliability of the large-top-mass limit.
• To explore the potential of azimuthal angle correlations as a probe of the tensor structure of the WWH coupling.

Proposed method

• Performs a next-to-leading-order QCD calculation of Higgs + 2 jet production via gluon fusion with full top-quark mass dependence using one-loop virtual and real emission diagrams.
• Compares results to the large-top-mass limit, where the top-quark loop is replaced by an effective Hgg vertex, reducing the calculation to two-loop order.
• Applies minimal and WBF-specific cuts: $p_{jot} > 20$ GeV, $|η_j| < 5$, $R_{jj} > 0.6$, and $m_{jj} > 600$ GeV to isolate weak-boson fusion events.
• Uses Monte Carlo integration with a factorization scale $\mu_f = \sqrt{p_{1\perp}p_{2\perp}}$ and $\alpha_s(M_Z) = 0.12$ to compute cross sections.
• Analyzes differential distributions in rapidity separation $\Delta\eta_{jj}$ and azimuthal angle $\phi_{jj}$ between the two jets to distinguish production mechanisms.
• Evaluates the sensitivity of the cross section to renormalization scale variations, finding strong dependence in the gluon-fusion channel.

Experimental results

Research questions

• RQ1 How accurate is the large-top-quark mass approximation for Higgs + 2 jet production in gluon fusion at the LHC?
• RQ2 To what extent do jet transverse momenta and dijet invariant masses invalidate the large-top-mass limit in the intermediate Higgs mass range?
• RQ3 Can rapidity separation between the two jets effectively suppress gluon-fusion contributions and enhance weak-boson fusion signals?
• RQ4 How do azimuthal angle correlations between the two jets differ between gluon-fusion and weak-boson fusion processes?
• RQ5 Can the azimuthal decorrelation distribution serve as a probe of anomalous WWH couplings beyond the Standard Model?

Key findings

• The large-top-quark mass limit provides an excellent approximation to the full top-quark mass calculation for Higgs masses below 200 GeV and jet transverse momenta below the top mass.
• The threshold enhancement at $m_H \approx 2m_t$ is well reproduced in both the full and large-top-mass calculations, confirming the robustness of the approximation in the high-mass region.
• With WBF-specific cuts, weak-boson fusion dominates over gluon fusion by a factor of about 3:1 for Higgs masses between 100 and 200 GeV.
• The rapidity separation between the two jets is significantly larger in weak-boson fusion than in gluon-fusion events, making it an effective discriminator.
• The azimuthal angle distribution in weak-boson fusion is flat, while in gluon fusion it exhibits a characteristic structure due to the CP-even $HG_{\mu\nu}G^{\mu\nu}$ coupling, enabling clear separation of the two mechanisms.
• The azimuthal decorrelation distribution can distinguish between CP-even and CP-odd anomalous WWH couplings, offering a probe of new physics beyond the Standard Model.