Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Combination of searches for nonresonant Higgs boson pair production in proton-proton collisions at $\sqrt{s}$= 13 TeV

CMS Collaboration

TL;DR

This CMS Run 2 study combines eight nonresonant Higgs boson pair searches at √s = 13 TeV using 138 fb^{-1} to constrain the inclusive HH cross section and Higgs self-couplings. The analysis employs a comprehensive signal modelling framework with coupling modifiers $\kappa_\lambda$, $\kappa_{2V}$, and HEFT parameters $c_2$, $c_g$, and $c_{2g}$, including an event-level reweighting strategy across HEFT benchmarks. The results yield a 95% CL upper limit of 3.5× the SM prediction on HH production and constrain $\kappa_\lambda$ to [−1.35, 6.37] and $\kappa_{2V}$ to [0.64, 1.40], with $\kappa_{2V}=0$ excluded at 6.6σ, illustrating evidence for quartic Higgs–vector interactions. The paper also maps HEFT results to UV-complete models and projects HL-LHC sensitivities, showing that up to 3000 fb^{-1} could yield meaningful constraints and potential evidence for HH production, thereby advancing our understanding of the Higgs self-interaction and possible new physics.

Abstract

This paper presents a combination of searches for the nonresonant production of Higgs boson pairs (HH) in proton-proton collisions at a centre-of-mass energy of 13 TeV. The data set was collected by the CMS experiment at the LHC from 2016 to 2018 and corresponds to a total integrated luminosity of 138 fb$^{-1}$. The observed (expected) upper limit on the inclusive HH production cross section relative to the standard model (SM) prediction is found to be 3.5 (2.5). Assuming all other Higgs boson couplings are equal to their SM values, the Higgs boson trilinear self-coupling modifier $κ_λ=λ_3/λ_{3}^\text{SM}$ is constrained in the range $-$1.35 $\leq$ $κ_λ$ $\leq$ 6.37 at 95% confidence level. Similarly, for the coupling modifier $κ_{2\mathrm{V}}$, which governs the interaction between two vector bosons and two Higgs bosons, we have excluded $κ_{2\mathrm{V}}$ = 0 at more than 5 standard deviations for all values of $κ_λ$. At 95% confidence level assuming other couplings are equal to their SM values, $κ_{2\mathrm{V}}$ is constrained in the range 0.64 $\leq$ $κ_{2\mathrm{V}}$ $\leq$ 1.40. This work also studies HH production in several new physics scenarios, using the Higgs effective field theory (HEFT) framework. The HEFT framework is further exploited to study various ultraviolet complete models with an extended Higgs sector and set constraints on specific parameters. An extrapolation of the results to the integrated luminosity expected after the high-luminosity upgrade of the LHC is reported as well.

Combination of searches for nonresonant Higgs boson pair production in proton-proton collisions at $\sqrt{s}$= 13 TeV

TL;DR

This CMS Run 2 study combines eight nonresonant Higgs boson pair searches at √s = 13 TeV using 138 fb^{-1} to constrain the inclusive HH cross section and Higgs self-couplings. The analysis employs a comprehensive signal modelling framework with coupling modifiers , , and HEFT parameters , , and , including an event-level reweighting strategy across HEFT benchmarks. The results yield a 95% CL upper limit of 3.5× the SM prediction on HH production and constrain to [−1.35, 6.37] and to [0.64, 1.40], with excluded at 6.6σ, illustrating evidence for quartic Higgs–vector interactions. The paper also maps HEFT results to UV-complete models and projects HL-LHC sensitivities, showing that up to 3000 fb^{-1} could yield meaningful constraints and potential evidence for HH production, thereby advancing our understanding of the Higgs self-interaction and possible new physics.

Abstract

This paper presents a combination of searches for the nonresonant production of Higgs boson pairs (HH) in proton-proton collisions at a centre-of-mass energy of 13 TeV. The data set was collected by the CMS experiment at the LHC from 2016 to 2018 and corresponds to a total integrated luminosity of 138 fb. The observed (expected) upper limit on the inclusive HH production cross section relative to the standard model (SM) prediction is found to be 3.5 (2.5). Assuming all other Higgs boson couplings are equal to their SM values, the Higgs boson trilinear self-coupling modifier is constrained in the range 1.35 6.37 at 95% confidence level. Similarly, for the coupling modifier , which governs the interaction between two vector bosons and two Higgs bosons, we have excluded = 0 at more than 5 standard deviations for all values of . At 95% confidence level assuming other couplings are equal to their SM values, is constrained in the range 0.64 1.40. This work also studies HH production in several new physics scenarios, using the Higgs effective field theory (HEFT) framework. The HEFT framework is further exploited to study various ultraviolet complete models with an extended Higgs sector and set constraints on specific parameters. An extrapolation of the results to the integrated luminosity expected after the high-luminosity upgrade of the LHC is reported as well.

Paper Structure

This paper contains 23 sections, 3 equations, 23 figures, 6 tables.

Table of Contents

  1. Introduction
  2. The CMS detector and event reconstruction
  3. Signal modelling
  4. Analysis strategy
  5. HH to bbbb
  6. HH to bbbb resolved
  7. HH to bbbb boosted
  8. VHH, HH to bbbb
  9. HH to bbtautau
  10. HH to bbgg
  11. HH to bbWW general
  12. HH to bbVV, VV to lnuqq/2l2nu
  13. HH to bbVV, VV to 4q
  14. HH to multilepton
  15. HH to tautaugammagamma
  16. ...and 8 more sections

Figures (23)

  • Figure 1: Leading-order Feynman diagrams of nonresonant Higgs boson pair production via gluon-gluon fusion in the SM. The modifiers of the Higgs boson coupling with the top quark and the Higgs boson trilinear self-coupling are shown as $\kappa_{{ \mathup{{{t}}{} _{ {}} ^{ {}}} }\xspace}$ and $\kappa_\lambda$, respectively.
  • Figure 2: Leading-order Feynman diagrams of nonresonant Higgs boson pair production via vector boson fusion in the SM. The modifiers of the Higgs boson coupling with a vector boson, the Higgs boson trilinear self-coupling, and the coupling between two Higgs bosons and two vector bosons are shown as $\kappa_{ \mathup{{{V}}{} _{ {}} ^{ {}}} }\xspace$, $\kappa_\lambda$, and $\kappa_{2{ \mathup{{{V}}{} _{ {}} ^{ {}}} }\xspace}$, respectively.
  • Figure 3: Leading-order Feynman diagrams of nonresonant Higgs boson pair production via associated production with a vector boson in the SM. The modifiers of the Higgs boson coupling with a vector boson, the Higgs boson trilinear self-coupling, and the coupling between two Higgs bosons and two vector bosons are shown as $\kappa_{ \mathup{{{V}}{} _{ {}} ^{ {}}} }\xspace$, $\kappa_\lambda$, and $\kappa_{2{ \mathup{{{V}}{} _{ {}} ^{ {}}} }\xspace}$, respectively.
  • Figure 4: Leading-order Feynman diagrams of nonresonant Higgs boson pair production via gluon-gluon fusion with anomalous Higgs boson couplings $\text{c}_2$, $\text{c}_{ \mathup{{{g}}{} _{ {}} ^{ {}}} }\xspace$, and $\text{c}_{2{ \mathup{{{g}}{} _{ {}} ^{ {}}} }\xspace}$. The Higgs boson trilinear self-coupling modifier is shown as $\kappa_\lambda$.
  • Figure 5: Illustrations of the resolved (upper left) and boosted (upper right) topologies of the ${ \mathup{{{b}}{} _{ {}} ^{ {}}} }\xspace{ \mathup{{ \overline{ {{ \mathup{{{b}}{} _{ {}} ^{ {}}} }\xspace}}}{} _{ {}} ^{ {}}} }\xspace\xspace{ \mathup{{{b}}{} _{ {}} ^{ {}}} }\xspace{ \mathup{{ \overline{ {{ \mathup{{{b}}{} _{ {}} ^{ {}}} }\xspace}}}{} _{ {}} ^{ {}}} }\xspace\xspace$ decay channel. The topology of ${ \mathup{{{V}}{} _{ {}} ^{ {}}} }\xspace{ \mathup{{{H}}{} _{ {}} ^{ {}}} }\xspace\xspace{ \mathup{{{H}}{} _{ {}} ^{ {}}} }\xspace\xspace$ production when all Higgs bosons decay to $\mathup{{{b}}{} _{ {}} ^{ {}}}$ jets and the vector boson is either a $\mathup{{{Z}}{} _{ {}} ^{ {}}}$ boson that decays into two leptons (lower left) or a $\mathup{{{W}}{} _{ {}} ^{ {}}}$ boson decaying into a lepton and a neutrino, giving missing transverse momentum (lower right).
  • ...and 18 more figures