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Boosting Higgs discovery - the forgotten channel

Christoph Hackstein, Michael Spannowsky

TL;DR

The paper investigates heavy Higgs searches in the $300$--$600$ GeV range, showing that a semi-leptonic channel $H \rightarrow ZZ \rightarrow (\ell\ell)(jj)$ reconstructed with fat-jet substructure can reach a discovery-scale significance. It develops a jet-substructure pipeline including fat jets, mass-drop, pruning, and trimming to reconstruct a hadronic $Z$ and combines it with a leptonic $Z$, achieving $S/B$ of roughly $0.3$--$0.9$ and a $5\sigma$ reach for $m_H$ in the 350--500 GeV window at 14 TeV with ~10 fb$^{-1}$. For 7 TeV data the channel alone is typically insufficient, but enhanced $ggH$ coupling in new physics scenarios can boost prospects. The semi-leptonic channel therefore provides a crucial, orthogonal discovery handle that complements the gold-plated leptonic mode, potentially enabling heavy-Higgs discovery under less-than-ideal LHC conditions.

Abstract

Searches for a heavy Standard Model Higgs boson focus on the 'gold plated mode' where the Higgs decays to two leptonic Z bosons. This channel provides a clean signature, in spite of the small leptonic branching ratios. We show that using fat jets the semi-leptonic ZZ mode significantly increases the number of signal events with a similar statistical significance as the leptonic mode.

Boosting Higgs discovery - the forgotten channel

TL;DR

The paper investigates heavy Higgs searches in the -- GeV range, showing that a semi-leptonic channel reconstructed with fat-jet substructure can reach a discovery-scale significance. It develops a jet-substructure pipeline including fat jets, mass-drop, pruning, and trimming to reconstruct a hadronic and combines it with a leptonic , achieving of roughly -- and a reach for in the 350--500 GeV window at 14 TeV with ~10 fb. For 7 TeV data the channel alone is typically insufficient, but enhanced coupling in new physics scenarios can boost prospects. The semi-leptonic channel therefore provides a crucial, orthogonal discovery handle that complements the gold-plated leptonic mode, potentially enabling heavy-Higgs discovery under less-than-ideal LHC conditions.

Abstract

Searches for a heavy Standard Model Higgs boson focus on the 'gold plated mode' where the Higgs decays to two leptonic Z bosons. This channel provides a clean signature, in spite of the small leptonic branching ratios. We show that using fat jets the semi-leptonic ZZ mode significantly increases the number of signal events with a similar statistical significance as the leptonic mode.

Paper Structure

This paper contains 4 sections, 5 equations, 3 figures, 2 tables.

Table of Contents

  1. Introduction
  2. The gold plated mode
  3. The semi-leptonic channel
  4. Conclusions

Figures (3)

  • Figure 1: Invariant mass distribution of the reconstructed $Z$ bosons in the semi-leptonic channel at 7 TeV (left) and 14 TeV (right) collider energy.
  • Figure 2: $p_{\rm T}$ distribution of the leading $Z$ boson for different Higgs masses $m_H$, assuming $\sqrt{s}=14~\rm{TeV}$.
  • Figure 3: Invariant mass distribution of the reconstructed $Z$ bosons, $m_{ZZ}$, in the semi-leptonic channel at $7$ TeV (left) and $14$ TeV (right) center-of-mass energy. A cut for the maximum angular separation of the $Z$ bosons has been applied, $\Delta R_{ Z_{\text{lep}},Z_{\text{had}} }$, as well as the combined usage of pruning and trimming. The signal consists of two parts. In every bin the top part shows the contribution of the WBF production process and the lower part the gluon fusion production process.