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Higgs + 2 jets via gluon fusion

V. Del Duca, W. Kilgore, C. Oleari, C. Schmidt, D. Zeppenfeld

TL;DR

This work addresses the challenge of distinguishing Higgs production via gluon fusion from weak-boson fusion in H+2 jet final states at the LHC by performing a complete real-emission calculation at $O(\alpha_s^4)$ that includes top-quark loop effects through triangle, box, and pentagon diagrams with arbitrary $m_t$. The amplitudes are computed analytically, reduced with Passarino–Veltman techniques, and validated against gauge invariance and the large-$m_t$ limit. Phenomenological results show sizable cross sections under minimal cuts and reveal a threshold enhancement near $m_H \approx 2 m_t$; under typical WBF tagging cuts, gluon fusion is suppressed relative to WBF by about a factor of three, enabling separation with a central-jet veto. Finite-$m_t$ effects are significant near threshold and at high jet $p_T$, while the heavy-top approximation remains reliable for moderate $p_T$ and sufficiently large partonic energy, informing Higgs-coupling extractions at the LHC.

Abstract

Real emission corrections to gg -> H, which lead to H+2 jet events, are calculated at order alpha_s^4. Contributions include top-quark triangles, boxes and pentagon diagrams and are evaluated analytically for arbitrary top mass m_t. This new source of H+2 jet events is compared to the weak-boson fusion cross section for a range of Higgs boson masses. The heavy top-mass approximation appears to work well for intermediate Higgs-boson masses, provided that the transverse momenta of the final-state partons are smaller than the top-quark mass.

Higgs + 2 jets via gluon fusion

TL;DR

This work addresses the challenge of distinguishing Higgs production via gluon fusion from weak-boson fusion in H+2 jet final states at the LHC by performing a complete real-emission calculation at that includes top-quark loop effects through triangle, box, and pentagon diagrams with arbitrary . The amplitudes are computed analytically, reduced with Passarino–Veltman techniques, and validated against gauge invariance and the large- limit. Phenomenological results show sizable cross sections under minimal cuts and reveal a threshold enhancement near ; under typical WBF tagging cuts, gluon fusion is suppressed relative to WBF by about a factor of three, enabling separation with a central-jet veto. Finite- effects are significant near threshold and at high jet , while the heavy-top approximation remains reliable for moderate and sufficiently large partonic energy, informing Higgs-coupling extractions at the LHC.

Abstract

Real emission corrections to gg -> H, which lead to H+2 jet events, are calculated at order alpha_s^4. Contributions include top-quark triangles, boxes and pentagon diagrams and are evaluated analytically for arbitrary top mass m_t. This new source of H+2 jet events is compared to the weak-boson fusion cross section for a range of Higgs boson masses. The heavy top-mass approximation appears to work well for intermediate Higgs-boson masses, provided that the transverse momenta of the final-state partons are smaller than the top-quark mass.

Paper Structure

This paper contains 4 sections, 3 equations, 3 figures.

Table of Contents

  1. Introduction
  2. Calculation
  3. Discussion of the results
  4. Conclusion

Figures (3)

  • Figure 1: Samples of Feynman graphs contributing to $H+2$ jet production via gluon fusion.
  • Figure 2: $H+2$ jet cross sections in pp collisions at $\sqrt{s}=14$ TeV as a function of the Higgs boson mass. Results are shown for gluon-fusion processes induced by a top-quark loop with $m_t=175$ GeV and in the $m_t\,\hbox{$\rightarrow$}\,\infty$ limit, computed using the heavy-top effective Lagrangian, and for weak-boson fusion. The two panels correspond to two sets of jet cuts: (a) inclusive selection (see Eq. (\ref{['eq:cuts_min']})) and (b) WBF selection (Eqs. (\ref{['eq:cuts_min']}) and (\ref{['eq:cut_gap']})).
  • Figure 3: Transverse-momentum distribution of the hardest jet in $H+2$ jet events from gluon-fusion processes. Jets are defined via the inclusive selection of Eq. (\ref{['eq:cuts_min']}). The two curves are for $m_t=175$ GeV and for the $m_t \,\hbox{$\rightarrow$}\,\infty$ limit, computed using the heavy-top effective Lagrangian. The mass of the Higgs is set to 120 GeV.