17,799 research outputs found
The minimal fermionic model of electroweak baryogenesis
We present the minimal model of electroweak baryogenesis induced by fermions.
The model consists of an extension of the Standard Model with one electroweak
singlet fermion and one pair of vector like doublet fermions with
renormalizable couplings to the Higgs. A strong first order phase transition is
radiatively induced by the singlet-doublet fermions, while the origin of the
baryon asymmetry is due to asymmetric reflection of the same set of fermions on
the expanding electroweak bubble wall. The singlet-doublet fermions are
stabilized at the electroweak scale by chiral symmetries and the Higgs
potential is stabilized by threshold corrections coming from a multi-TeV
ultraviolet completion which does not play any significant role in the phase
transition. We work in terms of background symmetry invariants and perform an
analytic semiclassical calculation of the baryon asymmetry, showing that the
model may effectively generate the observed baryon asymmetry for percent level
values of the unique invariant CP violating phase of the singlet-doublet
sector. We include a detailed study of electron electric dipole moment and
electroweak precision limits, and for one typical benchmark scenario we also
recast existing collider constraints, showing that the model is consistent with
all current experimental data. We point out that fermion induced electroweak
baryogenesis has irreducible phenomenology at the LHC
since the new fermions must be at the electroweak scale, have electroweak
quantum numbers and couple strongly with the Higgs. The most promising searches
involve topologies with multiple leptons and missing energy in the final state.Comment: 30 + 10 pages, 6 figure
Electroweak baryogenesis in the Z3-invariant NMSSM
We calculate the baryon asymmetry of the Universe in the Z3-invariant
Next-to-Minimal Supersymmetric Standard Model where the interactions of the
singlino provide the necessary source of charge and parity violation. Using the
closed time path formalism, we derive and solve transport equations for the
cases where the singlet acquires a vacuum expectation value (VEV) before and
during the electroweak phase transition. We perform a detailed scan to show how
the baryon asymmetry varies throughout the relevant parameter space. Our
results show that the case where the singlet acquires a VEV during the
electroweak phase transition typically generates a larger baryon asymmetry,
although we expect that the case where the singlet acquires a VEV first is far
more common for any model in which parameters unify at a high scale. Finally,
we examine the dependence of the baryon asymmetry on the three-body
interactions involving gauge singlets.Comment: 24 pages, version submitted to the journa
gravity in the early Universe: Electroweak phase transition and chameleon mechanism
It is widely believed that the screening mechanism is an essential feature
for the modified gravity theory. Although this mechanism has been examined
thoroughly in the past decade, their analyses are based on the classical
configuration of the matter fields. In this paper, we demonstrate a new
formulation of the chameleon mechanism in gravity theory, to shed light
on quantum-field theoretical effects on the chameleon mechanism as well as the
related scalaron physics, induced by the matter sector. We show a potential
absence of the chameleon mechanism in the cosmic history based on a
scale-invariant-extended scenario beyond the standard model of particle
physics, in which a realistic electroweak phase transition, possibly yielding
the right amount of baryon asymmetry of Universe today, simultaneously breaks
the scale invariance in the early Universe. Remarkably enough, the matter
sector contribution to the trace of energy-momentum tensor turns out to be on
the same order of magnitude as that computed in the classical perfect-fluid
approximation, even though the theory involves the nontrivial electroweak-phase
transition environment. We also briefly discuss the oscillation of the scalaron
field and indirect generation of non-tensorial gravitational waves induced by
the electroweak phase transition.Comment: 17 pages, 4 figures, version accepted in Chinese Physics
Gravitational waves from scale-invariant vector dark matter model: Probing below the neutrino-floor
We study the gravitational waves (GWs) spectrum produced during the
electroweak phase transition in a scale-invariant extension of the Standard
Model (SM), enlarged by a dark gauge symmetry. This symmetry
incorporates a vector dark matter (DM) candidate and a scalar field (scalon).
Because of scale invariance, the model has only two independent parameters and
for the parameter space constrained by DM relic density, strongly first-order
electroweak phase transition can take place. In this model, for a narrow part
of the parameter space, DM-nucleon cross section is below the neutrino-floor
limit, and therefore, it cannot be probed by the future direct detection
experiments. However, for a benchmark point form this narrow region, we show
the amplitude and frequency of phase transition GW spectrum fall within the
observational window of space-based GW detectors such as eLISA.Comment: 12 pages, 6 figures, references updated, version accepted for
publication in The European Physical Journal
Gravitational wave effects and phenomenology of a two-component dark matter model
We study an extension of the Standard Model (SM) which could have two
candidates for dark matter (DM) including a Dirac fermion and a Vector Dark
Matter (VDM) under new gauge group in the hidden sector. The model is
classically scale invariant and the electroweak symmetry breaks because of the
loop effects. We investigate the parameter space allowed by current
experimental constraints and phenomenological bounds. We probe the parameter
space of the model in the mass range GeV and
GeV. It has been shown that there are many points in this mass range that are
in agreement with all phenomenological constraints. The electroweak phase
transition have been discussed and shown that there is region in the parameter
space of the model consistent with DM relic density and direct detection
constraints, while at the same time can lead to first order electroweak phase
transition. The gravitational waves produced during the phase transition could
be probed by future space-based interferometers such as LISA and BBO.Comment: 28 pages, 11 figure
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