We calculate the spectrum of gravitational waves originated from strongly first order electroweak phase transition in the extended Higgs model with a real singlet scalar field. In order to calculate ...the bubble nucleation rate, we perform a two-field analysis and evaluate bounce solutions connecting the true and the false vacua using the one-loop effective potential at finite temperatures. Imposing the Sakharov condition of the departure from thermal equilibrium for baryogenesis, we survey allowed regions of parameters of the model. We then investigate the gravitational waves produced at electroweak bubble collisions in the early Universe, such as the sound wave, the bubble wall collision and the plasma turbulence. We find that the strength at the peak frequency can be large enough to be detected at future space-based gravitational interferometers such as eLISA, DECIGO and BBO. Predicted deviations in the various Higgs boson couplings are also evaluated at the zero temperature, and are shown to be large enough too. Therefore, in this model strongly first order electroweak phase transition can be tested by the combination of the precision study of various Higgs boson couplings at the LHC, the measurement of the triple Higgs boson coupling at future lepton colliders and the shape of the spectrum of gravitational wave detectable at future gravitational interferometers.
Abstract If fermionic dark matter (DM) is stabilized by dark U(1) gauge symmetry that is spontaneously broken into its subgroup Z 2, the particle contents of the model becomes very rich: DM and ...excited DM, both of them are Majorana fermions, as well as two dark force mediators, dark photon and dark Higgs boson are naturally present due to the underlying dark gauge symmetry. In this paper, we study the DM bound state formation processes within this scenario, assuming both dark photon and dark Higgs are light mediators and including the effects of excited DM. The Goldstone boson contributions to the potential matrix in the Schrödinger equations are found to be important. The emissions of a longitudinal vector boson (or somehow equivalently a Goldstone boson) during the DM bound state formations are crucial to induce a significant reannihilation process, reducing the dark matter relic abundance. Most of the stringent constraints for this kind of dark matter considered in the literature are simply evaded.
A
bstract
We consider a standard model extension equipped with a dark sector where the U(1)
X
Abelian gauge symmetry is spontaneously broken by the dark Higgs mechanism. In this framework, we ...investigate patterns of the electroweak phase transition as well as those of the dark phase transition, and examine detectability of gravitational waves (GWs) generated by such strongly first order phase transition. It is pointed out that the collider bounds on the properties of the discovered Higgs boson exclude a part of parameter space that could otherwise generate detectable GWs. After imposing various constraints on thi model, it is shown that GWs produced by multi-step phase transitions are detectable at future space-based interferometers, such as LISA and DECIGO, if the dark photon is heavier than 25 GeV. Furthermore, we discuss the complementarity of dark photon searches or dark matter searches with the GW observations in these models with the dark gauge symmetry.
A
bstract
As a new type of dynamical dark matter mechanism, we discuss the stability of the gauged Q-ball dark matter and its production mechanism through a cosmological first-order phase transition. ...This work delves into the study of gauged Q-ball dark matter generated during the cosmic phase transition. We demonstrate detailed discussions on the stability of gauged Q-balls to rigorously constrain their charge and mass ranges. Additionally, employing analytic approximations and the mapping method, we provide qualitative insights into gauged Q-balls. We establish an upper limit on the gauge coupling constant and give the relic density of stable gauged Q-ball dark matter formed during a first-order phase transition. Furthermore, we discuss potential observational signatures or constraints of gauged Q-ball dark matter, including astronomical observations and gravitational wave signals.
A
bstract
We investigate dark matter phenomenology and Higgs inflation in a dark U(1)
D
-extended model. The model features two dark matter candidates, a dark fermion and a dark vector boson. When ...the fermion dark matter
ψ
is heavier than the vector dark matter
W
D
, there is an ample parameter space where
ψ
is dominant over
W
D
. The model can then easily evade the stringent bounds from direct detection experiments, since
ψ
has no direct coupling to the Standard Model particles. Furthermore, the model can accommodate inflation in three different ways, one along the Standard Model Higgs direction, one along the dark Higgs direction, and one along the combination of the two. Considering the running of the parameters and various observational constraints, we perform a detailed numerical analysis and identify allowed parameter spaces that explain both dark matter and Higgs inflation in a unified manner. We discuss in detail how the imposition of Higgs inflation severely constrains the dark matter parameter space. The existence of the dark Higgs field is found to play a crucial role both in dark matter phenomenology and in generalised Higgs inflation.
Abstract Multi-component dark matter scenarios are studied in the model with U(1) X dark gauge symmetry that is broken into its product subgroup Z 2 × Z 3 á la Krauss-Wilczek mechanism. In this ...setup, there exist two types of dark matter fields, X and Y, distinguished by different Z 2 × Z 3 charges. The real and imaginary parts of the Z 2-charged field, X R and X I , get different masses from the U(1) X symmetry breaking. The field Y, which is another dark matter candidate due to the unbroken Z 3 symmetry, belongs to the Strongly Interacting Massive Particle (SIMP)-type dark matter. Both X I and X R may contribute to Y’s 3 → 2 annihilation processes, opening a new class of SIMP models with a local dark gauge symmetry. Depending on the mass difference between X I and X R , we have either two-component or three-component dark matter scenarios. In particular two- or three-component SIMP scenarios can be realised not only for small mass difference between X and Y, but also for large mass hierarchy between them, which is a new and unique feature of the present model. We consider both theoretical and experimental constraints, and present four case studies of the multi-component dark matter scenarios.
A
bstract
In this paper, we construct for the first time a two-component strongly interacting massive particles (SIMP) dark matter (DM) model, where a complex scalar and a vector-like fermion play ...the role of the SIMP DM candidates. These two particles are stable due to an accidental ℤ
4
symmetry after the breaking of a U(1)
D
gauge symmetry. By introducing one extra complex scalar as a mediator between the SIMP particles, this model can have 3 → 2 processes that determine the DM relic density. On the other hand, the SIMP DM particles can maintain kinetic equilibrium with the thermal bath until the DM freeze-out temperature via the U(1)
D
gauge couplings. Most importantly, we find an unavoidable two-loop induced 2 → 2 process tightly connecting to the 3 → 2 process that would redistribute the SIMP DM number densities after the chemical freeze-out of DM. Moreover, this redistribution would significantly modify the predictions of the self-interacting cross section of DM compared with other SIMP models. It is crucial to include the two-loop induced 2 → 2 annihilations to obtain the correct DM phenomenology.
A
bstract
Multi-component dark matter scenarios are studied in the model with U(1)
X
dark gauge symmetry that is broken into its product subgroup
Z
2
×
Z
3
á la Krauss-Wilczek mechanism. In this ...setup, there exist two types of dark matter fields,
X
and
Y
, distinguished by different
Z
2
×
Z
3
charges. The real and imaginary parts of the
Z
2
-charged field,
X
R
and
X
I
, get different masses from the U(1)
X
symmetry breaking. The field
Y
, which is another dark matter candidate due to the unbroken
Z
3
symmetry, belongs to the Strongly Interacting Massive Particle (SIMP)-type dark matter. Both
X
I
and
X
R
may contribute to
Y
’s 3 → 2 annihilation processes, opening a new class of SIMP models with a local dark gauge symmetry. Depending on the mass difference between
X
I
and
X
R
, we have either two-component or three-component dark matter scenarios. In particular two- or three-component SIMP scenarios can be realised not only for small mass difference between
X
and
Y
, but also for large mass hierarchy between them, which is a new and unique feature of the present model. We consider both theoretical and experimental constraints, and present four case studies of the multi-component dark matter scenarios.
Beauty tetraquark states X(b¯q′q″q¯) composed of b¯sud¯, b¯dsu¯, and b¯uds¯, are unique that all the four valence quarks are different. Although the claim of existence of the first two states by D0 ...was not confirmed by data from LHCb, the possibility of such states still generated a lot of interests and should be pursued further. Non-observation of X(b¯q′q″q¯) states by LHCb may be just due to a still lower production rate than the limit of LHCb or at some different mass ranges. In this work we use light quark SU(3) flavor symmetry as guideline to classify symmetry properties of beauty tetraquark states. The multiplets which contain states with three different light quarks must be one of 6¯ or 15 of SU(3) representations. We study possible decays of such a tetraquark state into a B meson and a light pseudoscalar octet meson by constructing a leading order chiral Lagrangian, and also provide search strategies to determine whether a given tetraquark state of this type belongs to 6¯ or 15. If X(b¯q′q″q¯) belongs to 15, there are new doubly charged tetraquark states b¯uud¯ and b¯uus¯.
A
bstract
We propose a deep learning-based search strategy for pair production of doubly charged scalars undergoing three-body decays to
W
+
t
b
¯
in the same-sign lepton plus multi-jet final state. ...This process is motivated by composite Higgs models with an underlying fermionic UV theory. We demonstrate that for such busy final states, jet image classification with convolutional neural networks outperforms standard fully connected networks acting on reconstructed kinematic variables. We derive the expected discovery reach and exclusion limit at the high-luminosity LHC.
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