Higgs pair production in the composite Higgs model

We propose a new type of search for a pseudoscalar particle \etaη pair produced via an off-shell Higgs, pp\to h^*\to \eta\etapp→h*→ηη. The search is motivated by a composite Higgs model in which the \etaη is extremely narrow and decays almost exclusively into Z\gammaZγ in the mass range 65{\mathrm{GeV}}\lesssim m_\eta \lesssim 160{\mathrm{GeV}}65GeV≲mη≲160GeV. We devise an analysis strategy to observe the novel Z\gamma Z\gammaZγZγ channel and estimate potential bounds on the Higgs-\etaη coupling. The experimental sensitivity to the signatures depends on the power to identify fake photons and on the ability to predict large photon multiplicities. This search allows us to exclude large values of the compositeness scale ff, being thus complementary to other typical processes.

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Electroweak baryogenesis and gravitational waves in a composite Higgs model with high dimensional fermion representations

Journal of High Energy Physics ◽

10.1007/jhep12(2020)047 ◽

2020 ◽

Vol 2020 (12) ◽

Author(s):

Ke-Pan Xie ◽

Ligong Bian ◽

Yongcheng Wu

Keyword(s):

Form Factors ◽

Higgs Doublet ◽

Higgs Model ◽

High Dimensional ◽

Electroweak Phase Transition ◽

First Order ◽

Composite Higgs ◽

Future Space ◽

The Universe ◽

Scalar Sector

Abstract We study electroweak baryogenesis in the SO(6)/SO(5) composite Higgs model with the third generation quarks being embedded in the 20′ representation of SO(6). The scalar sector contains one Higgs doublet and one real singlet, and their potential is given by the Coleman-Weinberg potential evaluated from the form factors of the lightest vector and fermion resonances. We show that the resonance masses at $$ \mathcal{O}\left(1\sim 10\kern0.5em \mathrm{TeV}\right) $$ O 1 ∼ 10 TeV can generate a potential that triggers the strong first-order electroweak phase transition (SFOEWPT). The CP violating phase arising from the dimension-6 operator in the top sector is sufficient to yield the observed baryon asymmetry of the universe. The SFOEWPT parameter space is detectable at the future space-based detectors.

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A composite Higgs with a heavy composite axion

Journal of High Energy Physics ◽

10.1007/jhep12(2020)094 ◽

2020 ◽

Vol 2020 (12) ◽

Author(s):

Tony Gherghetta ◽

Minh D. Nguyen

Keyword(s):

Cp Violation ◽

Gauge Group ◽

Scalar Fields ◽

Higgs Model ◽

Global Symmetry ◽

Color Group ◽

High Scale ◽

Axion Mass ◽

Composite Higgs ◽

The Standard Model

Abstract We consider the strong dynamics associated with a composite Higgs model that simultaneously produces dynamical axions and solves the strong CP problem. The strong dynamics arises from a new Sp or SU(4) hypercolor gauge group containing QCD colored hyperfermions that confines at a high scale. The hypercolor global symmetry is weakly gauged by the Standard Model electroweak gauge group and an enlarged color group, SU(N + 3) × SU(N)′. When hyperfermion condensates form, they not only lead to an SU(5)/SO(5) composite Higgs model but also spontaneously break the enlarged color group to SU(3)c× SU(N)D. At lower energies, the SU(N)D group confines, producing two dynamical axions that eliminates all CP violation. Furthermore, small instantons from the SU(N)′ group can enhance the axion mass, giving rise to TeV scale axion masses that can be detected at collider experiments. Our model provides a way to unify the composite Higgs with dynamical axions, without introducing new elementary scalar fields, while also extending the range of axion masses that addresses the strong CP problem.

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A more natural composite Higgs model

Journal of High Energy Physics ◽

10.1007/jhep10(2020)175 ◽

2020 ◽

Vol 2020 (10) ◽

Author(s):

Hsin-Chia Cheng ◽

Yi Chung

Keyword(s):

Standard Model ◽

Higgs Model ◽

Quadratic Term ◽

Beyond The Standard Model ◽

Higgs Potential ◽

Little Higgs ◽

Composite Higgs ◽

Partial Compositeness ◽

Quartic Term ◽

Natural Composite

Abstract Composite Higgs models provide an attractive solution to the hierarchy problem. However, many realistic models suffer from tuning problems in the Higgs potential. There are often large contributions from the UV dynamics of the composite resonances to the Higgs potential, and tuning between the quadratic term and the quartic term is required to separate the electroweak breaking scale and the compositeness scale. We consider a composite Higgs model based on the SU(6)/Sp(6) coset, where an enhanced symmetry on the fermion resonances can minimize the Higgs quadratic term. Moreover, a Higgs quartic term from the collective symmetry breaking of the little Higgs mechanism can be realized by the partial compositeness couplings between elementary Standard Model fermions and the composite operators, without introducing new elementary fields beyond the Standard Model and the composite sector. The model contains two Higgs doublets, as well as several additional pseudo-Nambu-Goldstone bosons. To avoid tuning, the extra Higgs bosons are expected to be relatively light and may be probed in the future LHC runs. The deviations of the Higgs couplings and the weak gauge boson couplings also provide important tests as they are expected to be close to the current limits in this model.

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