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Higgs boson self-couplings at the LHC as a probe of extended Higgs sectors

M. Moretti, S. Moretti, F. Piccinini, R. Pittau, A. D. Polosa

TL;DR

This work investigates Higgs self-couplings at the LHC as probes of extended Higgs sectors, focusing on two-Higgs-doublet models in the decoupling limit where the lightest Higgs may exhibit a large triple-self-coupling λ_{HHH} while other couplings remain SM-like. It analyzes Higgs-pair production with an intermediate-mass Higgs (M_H ≈ 120–140 GeV) through vector-boson fusion, Higgs-strahlung, and heavy-quark associated production, all decaying to bb, using a model-independent rescaling approach validated against full 2HDM calculations. The study shows that while SM HH production is challenging to observe, deviations in λ_{HHH} can yield detectable signals, particularly in VV fusion, and can thus reveal non-SM Higgs structure even when single-Higgs channels show SM-like behavior. These results imply that Higgs-pair production, especially in the 4b final state, could provide a crucial window into extended Higgs sectors at the LHC and its high-luminosity upgrade.

Abstract

A study of two-Higgs-doublet models (2HDM) in the decoupling limit reveals the existence of parameter configurations with a large triple-Higgs self-coupling as the only low-energy trace of the departure from a Standard Model (SM) Higgs sector. This observation encourages attempts to search for double Higgs production at the Large Hadron Collider (LHC) even in mass regions which have been shown to be very hard to probe in the context of SM-like Higgs self-couplings. In this document we consider the case of an Intermediate Mass Higgs (IMH) boson, with 120 GeV <= M_H <= 140 GeV, produced in pairs via vector-vector fusion, Higgs-strahlung and associate production with heavy-quarks and decaying into b anti-b pairs. After a detailed signal-to-background analysis, we confirm that the observation of a Higgs-pair signal is very challenging in the framework of the SM, even at the LHC with upgraded luminosity. In contrast, we verify that the sensitivity is sufficient to detect departures from the SM which would escape detection in the measurements of the single-Higgs production channels.

Higgs boson self-couplings at the LHC as a probe of extended Higgs sectors

TL;DR

This work investigates Higgs self-couplings at the LHC as probes of extended Higgs sectors, focusing on two-Higgs-doublet models in the decoupling limit where the lightest Higgs may exhibit a large triple-self-coupling λ_{HHH} while other couplings remain SM-like. It analyzes Higgs-pair production with an intermediate-mass Higgs (M_H ≈ 120–140 GeV) through vector-boson fusion, Higgs-strahlung, and heavy-quark associated production, all decaying to bb, using a model-independent rescaling approach validated against full 2HDM calculations. The study shows that while SM HH production is challenging to observe, deviations in λ_{HHH} can yield detectable signals, particularly in VV fusion, and can thus reveal non-SM Higgs structure even when single-Higgs channels show SM-like behavior. These results imply that Higgs-pair production, especially in the 4b final state, could provide a crucial window into extended Higgs sectors at the LHC and its high-luminosity upgrade.

Abstract

A study of two-Higgs-doublet models (2HDM) in the decoupling limit reveals the existence of parameter configurations with a large triple-Higgs self-coupling as the only low-energy trace of the departure from a Standard Model (SM) Higgs sector. This observation encourages attempts to search for double Higgs production at the Large Hadron Collider (LHC) even in mass regions which have been shown to be very hard to probe in the context of SM-like Higgs self-couplings. In this document we consider the case of an Intermediate Mass Higgs (IMH) boson, with 120 GeV <= M_H <= 140 GeV, produced in pairs via vector-vector fusion, Higgs-strahlung and associate production with heavy-quarks and decaying into b anti-b pairs. After a detailed signal-to-background analysis, we confirm that the observation of a Higgs-pair signal is very challenging in the framework of the SM, even at the LHC with upgraded luminosity. In contrast, we verify that the sensitivity is sufficient to detect departures from the SM which would escape detection in the measurements of the single-Higgs production channels.

Paper Structure

This paper contains 9 sections, 6 equations, 3 figures.

Table of Contents

  1. Introduction
  2. Higgs-pair production at the LHC
  3. The decoupling limit of 2HDMs
  4. Triple-Higgs self-couplings at the LHC
  5. Vector-vector fusion
  6. Higgs-strahlung
  7. Heavy-quark associate production
  8. Discussion of the results
  9. Summary and outlook

Figures (3)

  • Figure 1: Shapes of the integrated distributions of the minimum (left) and next-to-minimum (right) $bb$ invariant masses in vector-vector fusion and relative QCD background, after the application of the cuts discussed in the text up to Eq. (\ref{['eq:mhchi2']}). Both signal and noise are shown for the case $M_H=120$ GeV.
  • Figure 2: Shapes of the differential (up) and integrated (down) distributions of the minimum forward/backward jet transverse momentum in vector-vector fusion and relative QCD background, after the application of the cuts discussed in the text up to Eq. (\ref{['eq:mhchi2']}) Both signal and noise are shown for the case $M_H=120$ GeV.
  • Figure 3: Shape of the distribution of $M$ in Eq. (\ref{['Mdist']}) for the case $M_H=120$ GeV (left) and $M_H=200$ GeV (right).