<p>We propose a novel scale-invariant model with the 3-3-1-1 gauge symmetry featuring a universal seesaw mechanism for all fermion masses, which, through the inclusion of additional vectorlike quarks, provides a partial explanation for the observed fermion mass hierarchies. A discrete remnant of the gauge group, the matter parity (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>P</mi><mi>M</mi></msub></math>), stabilizes a fermionic dark matter candidate, and the scalar sector includes two triplets (minimal for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>3</mn><mtext>−</mtext><mn>3</mn><mtext>−</mtext><mn>1</mn></mrow></math> breaking) and two scalar singlets. We identify the lightest <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>P</mi><mi>M</mi></msub></math>-odd fermion, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mi mathvariant="normal">d</mi></msub></math>, as a viable dark matter candidate. Our analysis shows that <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mi mathvariant="normal">d</mi></msub></math> satisfies the observed relic density constraint within the mass range <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>220</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi><mo>≲</mo><msub><mi>m</mi><msub><mi>f</mi><mi mathvariant="normal">d</mi></msub></msub><mo>≲</mo><mn>555</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, primarily due to resonant annihilation via the new scalar <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>H</mi><mn>2</mn></msub></math>. While this mass range depends on the symmetry-breaking scale <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>v</mi><mi>χ</mi></msub></math>, which has a lower bound of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>v</mi><mi>χ</mi></msub><mo>≳</mo><mn>3.6</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math> from LEP constraints on the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>ρ</mi><mn>0</mn></msub></math> parameter, we adopt a more conservative lower bound of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>v</mi><mi>χ</mi></msub><mo>&gt;</mo><mn>10</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>. This choice is made to ensure that the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Z</mi><mo>′</mo></msup></math> boson mass remains above approximately 4 TeV, and is motivated by recent LHC results and future projections for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Z</mi><mo>′</mo></msup></math> boson searches, which provide more stringent constraints than previous bounds or those from the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>ρ</mi><mn>0</mn></msub></math> parameter. Spin-independent (SI) interactions dominate the direct detection phenomenology of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mi mathvariant="normal">d</mi></msub></math>. We calculate the SI elastic scattering cross section and find that parameter points satisfying the relic density constraint are consistent with current experimental limits from LZ and PandaX-4T for certain parameter choices, particularly depending on the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>α</mi><mn>12</mn></msub></math> angle. Some regions of the viable parameter space lie below the neutrino floor. Prospects for detection by future experiments like XLZD and PandaX-xT are also presented and discussed.</p>

Brazil

Alex G. Dias

Vinicius Padovani

Estonia

Kristjan Kannike

Niko Koivunen

Spain

Julio Leite

B.L. Sánchez-Vega

Dark matter in the scale-invariant 3-3-1-1 model

Theories with more than one scalar field often exhibit phase transitions producing potentially detectable gravitational wave (GW) signal. In this work we study the semi-annihilating ℤ 3 dark matter model, whose dark sector comprises an inert doublet and a complex singlet, and assess its prospects in future GW detectors. Without imposing limits from requirement of providing a viable dark matter candidate, i.e. taking into account only other experimental and theoretical constraints, we find that the first order phase transition in this model can be strong enough to lead to a detectable signal. However, direct detection and the dark matter thermal relic density constraint calculated with the state-of-the-art method including the impact of early kinetic decoupling, very strongly limit the parameter space of the model explaining all of dark matter and providing observable GW peak amplitude. Extending the analysis to underabundant dark matter thus reveals region with detectable GWs from a single-step or multi-step phase transition.

Nico Benincasa

Poland

Andrzej Hryczuk

Maxim Laletin

Phase transitions and gravitational waves in a model of ℤ 3 scalar dark matter

We perform a comprehensive study of a model in which the Higgs sector is extended to contain two Higgs doublet fields, with the four types of possibilities to couple to standard fermions, as well as an additional light pseudoscalar Higgs boson which mixes with the one of the two doublets. This two-Higgs-doublet-plus-pseudoscalar model includes also a stable isosinglet massive fermion that has the correct thermal relic abundance to account for the dark matter in the Universe. We summarize the theoretical constraints to which the model is subject and then perform a detailed study of the phenomenological constraints. In particular, we discuss the bounds from the LHC in the search for light and heavy scalar resonances and invisible states and those from high-precision measurements in the Higgs, electroweak, and flavor sectors, addressing the possibility of explaining the deviation from the standard expectation of the anomalous magnetic moment of the muon and the <math><mi>W</mi></math>-boson mass recently observed at Fermilab. We also summarize the astrophysical constraints from direct and indirect detection dark matter experiments. We finally conduct a thorough analysis of the cosmic phase transitions and the gravitational wave spectrum that are implied by the model and identify the parameter space in which the electroweak vacuum is reached after single and multiple phase transitions. We then discuss the prospects for observing the signal of such gravitational waves in near-future experiments such as the Laser Interferometer Space Antenna, Big Bang Observer, or Deci-hertz Interferometer Gravitational wave Observatory.

Italy

Giorgio Arcadi

Abdelhak Djouadi

Two-Higgs-doublet-plus-pseudoscalar model: Collider, dark matter, and gravitational wave signals

The questions of the origin of electroweak symmetry breaking and neutrino mass are two major puzzles in particle physics. Neutrino mass generation requires new physics beyond the Standard Model and also suggests reconsideration of physics of symmetry breaking. The aim of this paper is to study radiative symmetry breaking in the singlet scalar extension of type II seesaw neutrino mass model. We derive bounded-from-below conditions for the scalar potential of the model in full generality for the first time. The Gildener–Weinberg approach is utilised in minimising the multiscalar potential. Upon imposing the bounded-from-below and perturbativity conditions, as well as experimental constraints from colliders, we find the parameter space of scalar quartic couplings that can radiatively realise electroweak symmetry breaking at one-loop level. To satisfy all the constraints, the masses of the heavy triplet-like Higgs bosons must be nearly degenerate. The evolution of the Higgs doublet quartic coupling  $$\lambda _{H}$$  <math> <msub> <mi>λ</mi> <mi>H</mi> </msub> </math>   can be prevented from being negative up to the Planck scale.

Thailand

Bayu Dirgantara

Warintorn Sreethawong

Vacuum stability and radiative symmetry breaking of the scale-invariant singlet extension of type II seesaw model

We consider the classically scale invariant Higgs-dilaton model of dynamical symmetry breaking extended with an extra scalar field that plays the role of dark matter. The Higgs boson is light near a critical boundary between different symmetry breaking phases, where quantum corrections beyond the usual Gildener-Weinberg approximation become relevant. This implies a tighter connection between dark matter and Higgs phenomenology. The model has only three free parameters, yet it allows for the observed relic abundance of dark matter while respecting all constraints. The direct detection cross section mediated by the Higgs boson is determined by the dark matter mass alone and is testable at future experiments.

Aleksei Kubarski

Luca Marzola

Martti Raidal

Alessandro Strumia

Venno Vipp

Dark matter-induced multi-phase dynamical symmetry breaking

The recently proposed multiphase criticality principle in Coleman-Weinberg models can provide a new explanation for the hierarchy between the electroweak and new physics scales. When applied to the Standard Model, a Higgs boson as light as the pseudo-Goldstone boson of broken-scale invariance occurs. The suppressed mixing between the two light fields still carries information about the large scale of symmetry breaking, albeit up to logarithmic corrections. In this work we probe this scenario with the present LHC data and assess the impact of future lepton and hadron colliders. Our results show that the multiphase criticality can easily explain the apparent absence of new physics at the energy scales tested in current experiments.

Finland

Katri Huitu

India

Subhadeep Mondal

Multiphase critical Higgs boson at colliders

We derive the vacuum stability conditions for a left-right-symmetric potential more general than originally considered.

Addendum to: Vacuum stability conditions and potential minima for a matrix representation in lightcone orbit space

The orbit space for a scalar field in a complex square matrix representation obtains a Minkowski space structure from the Cauchy–Schwarz inequality. It can be used to find vacuum stability conditions and minima of the scalar potential. The method is suitable for fields such as a bidoublet, an SU(2) triplet or SU(3) octet. We use the formalism to find the vacuum stability conditions for the left-right symmetric potential of a bidoublet and left and right Higgs doublets.

Vacuum stability conditions and potential minima for a matrix representation in lightcone orbit space

We introduce a new way of modeling the physics beyond the Standard Model by considering fake, strictly off-shell degrees of freedom: the fakeons. To demonstrate the approach and exemplify its reach, we re-analyze the phenomenology of the Inert Doublet Model under the assumption that the second doublet is a fakeon. Remarkably, the fake doublet avoids the most stringent Z-pole constraints regardless of the chosen mass scale, thereby allowing for the presence of new effects well below the electroweak scale. Furthermore, the absence of on-shell propagation prevents fakeons from inducing missing energy signatures in collider experiments. The distinguishing features of the model appear at the loop level, where fakeons modify the Higgs boson h → γγ decay width and the Higgs trilinear coupling. The running of Standard Model parameters proceeds as in the usual Inert Doublet Model case. Therefore, the fake doublet can also ensure the stability of the Standard Model vacuum. Our work shows that fakeons are a valid alternative to the usual tools of particle physics model building, with the potential to shape a new paradigm, where the significance of the existing experimental constraints towards new physics must necessarily be reconsidered.

Damiano Anselmi

Carlo Marzo

Aurora Melis

Kristjan Müürsepp

Marco Piva

Phenomenology of a fake Inert Doublet Model

The principle of multiple point criticality (PMPC), which allowed the prediction of the Higgs boson mass before its discovery, has so far been applied to radiatively generated vacua. If this principle is fundamental, following from some presently unknown underlying physics, the PMPC must apply to all vacua, including the multiple vacua of multi-scalar models dominated by tree-level terms. We first motivate this idea and then exemplify it by applying the PMPC to various realizations of singlet scalar dark matter models. We derive constraints on the dark matter properties from the requirement of degenerate vacua and show that some scalar dark matter models are ruled out by the PMPC, while in others the allowed parameters space is constrained.

Principle of multiple point criticality in multi-scalar dark matter models