Higgs pair production in vector-boson fusion at the LHC and beyond

TL;DR

This work investigates Higgs pair production via vector-boson fusion as a probe of the hhVV coupling, using an EFT framework with cV, c2V and related parameters. It develops a boosted bb̄bb̄ analysis with scale-invariant jet substructure tagging to reconstruct di-Higgs events and suppress QCD backgrounds, quantifying sensitivity to δc2V across 14 TeV LHC, HL-LHC, and a future 100 TeV collider. The results show that δc2V can be constrained at the tens of percent level at the LHC and reach percent-level precision at 100 TeV, with the tail of the m_hh distribution driving the sensitivity. The study also addresses EFT validity, background modeling, and potential improvements (MVA, extra EFT operators, detector effects) for future work. Overall, vector-boson fusion di-Higgs production provides a complementary pathway to probe the Higgs sector and EWSB dynamics beyond gluon-fusion channels.

Abstract

The production of pairs of Higgs bosons at hadron colliders provides unique information on the Higgs sector and on the mechanism underlying electroweak symmetry breaking (EWSB). Most studies have concentrated on the gluon fusion production mode which has the largest cross section. However, despite its small production rate, the vector-boson fusion channel can also be relevant since even small modifications of the Higgs couplings to vector bosons induce a striking increase of the cross section as a function of the invariant mass of the Higgs boson pair. In this work, we exploit this unique signature to propose a strategy to extract the $hhVV$ quartic coupling and provide model-independent constraints on theories where EWSB is driven by new strong interactions. We take advantage of the higher signal yield of the $b\bar b b\bar b$ final state and make extensive use of jet substructure techniques to reconstruct signal events with a boosted topology, characteristic of large partonic energies, where each Higgs boson decays to a single collimated jet . Our results demonstrate that the $hhVV$ coupling can be measured with 45% (20%) precision at the LHC for $\mathcal{L}=$ 300 (3000) fb$^{-1}$, while a 1% precision can be achieved at a 100 TeV collider.

Figures (17)

• Figure 1: Tree-level Feynman diagrams contributing to Higgs pair production via VBF. In terms of Eq. (\ref{['eq:lagrangian']}), the left, middle, and right diagrams scale with $c_{2V}$, $c_V^2$, and $c_{V}c_3$, respectively.
• Figure 2: Schematic representation of the analysis strategy adopted in this work.
• Figure 3: Distribution of the rapidity separation $|\Delta y_{jj}|$ (upper) and the invariant mass $m_{jj}$ (bottom panels) of the VBF tagging jets at 14 TeV (left) and 100 TeV (right panels), for signal (SM and $c_{2V}=0.8$) and background events after the acceptance cuts. The vertical line indicates the value of the corresponding cut from Table \ref{['tab:sel-cuts']}. The distributions have been area-normalized and rescaled by a common factor.
• Figure 4: Distribution of the pseudo-rapidity $|\eta_j^{\rm max}|$ of the most forward light jet at $14\,$TeV and $100\,$TeV. Both curves have a discontinuity at the edge of the corresponding b-tagging region which is delineated by the solid (dashed) grey vertical lines in the case of 14 (100) TeV. This discontinuity is more clearly visible in the 100 TeV curve and is purely due to combinatorics.
• Figure 5: Distributions of the $p_T$ of the leading, subleading, and 3rd light jet at $14\,$TeV (left panel) and $100\,$TeV (right panel) for the SM signal. Distributions are area-normalized as in Fig. \ref{['fig:dyljets']}.