Leptogenesis in a model of Dark Energy and Dark Matter (original) (raw)
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Dark CP violation and gauged lepton or baryon number for electroweak baryogenesis
Physical Review D, 2020
We explore the generation of the baryon asymmetry in an extension of the Standard Model where the lepton number is promoted to a U (1) gauge symmetry with an associated Z gauge boson. This is based on a novel electroweak baryogenesis mechanism first proposed by us in Ref. [1]. Extra fermionic degrees of freedom-including a fermionic dark matter χ-are introduced in the dark sector for anomaly cancellation. Lepton number is spontaneously broken at high scale and the effective theory, containing the Standard Model, the Z , the fermionic dark matter, and an additional complex scalar field S, violates CP in the dark sector. The complex scalar field couples to the Higgs portal and is essential in enabling a strong first order phase transition. Dark CP violation is diffused in front of the bubble walls and creates a chiral asymmetry for χ, which in turn creates a chemical potential for the Standard Model leptons. Weak sphalerons are then in charge of transforming the net lepton charge asymmetry into net baryon number. We explore the model phenomenology related to the leptophilic Z , the dark matter candidate, the Higgs boson and the additional scalar, as well as implications for electric dipole moments. We also discuss the case when baryon number U (1) B is promoted to a gauge symmetry, and discuss electroweak baryogenesis and its corresponding phenomenology.
Shadow fermions, messenger scalars and leptogenesis
Nuclear Physics B, 2009
A mechanism for leptogenesis at the electroweak scale was investigated in a model of dark energy and dark matter proposed by one of us (PQH). This model involves an asymptotically free gauge group SU (2) Z and an axion-like particle with an SU (2) Z-instanton-induced potential which yields a scenario for the dark energy. Furthermore, the extended particle content of this SU (2) Z model contains a possible candidate for the cold dark matter, namely, the SU (2) Z "shadow" fermion, which couples with the Standard Model lepton through a scalar "messenger field" carrying both SU (2) Z and electroweak quantum numbers. Since these shadow fermions are in a real representation of SU (2) Z , lepton number can be violated in the Yukawa sector and a lepton number asymmetry can be generated in the SU (2) Z particle's decay which is also CP-violating and "out-of-equilibrium". The asymmetry coming from the interference between the tree-level and one-loop amplitudes was calculated for both messenger scalar and shadow fermion decays. It turns out, in order to have a non-vanishing lepton asymmetry and to be consistent with the unitarity condition, some shadow fermions have to decay into lighter messenger scalars, hence could be a candidate "progenitor" for the lepton asymmetry.
Brazilian Journal of Physics, 2016
We propose a mirror model for ordinary and dark matter that assumes a new SU(3) gauge group of transformations, as a natural extension of the Standard Model (SM). A close study of big bang nucleosynthesis, baryon asymmetries, cosmic microwave background bounds, galaxy dynamics, together with the Standard Model assumptions, help us to set a limit on the mass and width of the new gauge boson. The cross section for the elastic scattering of a dark proton by an ordinary proton is estimated and compare to the WIMP-nucleon experimental upper bounds. It is observed that all experimental bounds for the various cross sections can be accommodated consistently within the gauge model. We also suggest a way for direct detection of the new gauge boson via one example of a SM forbidden process: e + + p → µ + + X, where X = Λ or Λc.
Constraints on mass dimension one fermionic dark matter from the Yukawa interaction
Physical Review D, 2016
We study the loop corrections to the scalar propagator and the fermionic self-energy for the mass dimension one fermionic dark matter with the Yukawa interaction. We find, in the former case, there is a non-vanishing Lorentz-violating term while the later is Lorentz-invariant. Our study of the fermionic loop correction shows that unitarity demands the fermionic mass must be at least half of the bosonic mass and that the Lorentz-violating term makes a non-trivial correction to the bosonic propagator. We discuss what these results mean in the context of the Standard Model and the possibility of bypassing the unitarity constraint. In the simplest scenario, within the framework of standard quantum field theory, by identifying the scalar boson to be the Higgs boson with a mass of 125 GeV, the mass of the fermion must be at least 62.5 GeV.
Electroweak baryogenesis, large Yukawas and dark matter
Journal of High Energy Physics, 2005
It has recently been shown that the electroweak baryogenesis mechanism is feasible in Standard Model extensions containing extra fermions with large Yukawa couplings. We show here that the lightest of these fermionic fields can naturally be a good candidate for cold dark matter. We find regions in the parameter space where the thermal relic abundance of this particle is compatible with the dark matter density of the Universe as determined by the WMAP experiment. We study direct and indirect dark matter detection for this model and compare with current experimental limits and prospects for upcoming experiments. We find, contrary to the standard lore, that indirect detection searches are more promising than direct ones, and they already exclude part of the parameter space.
Dark matter coupling to electroweak gauge and Higgs bosons: An effective field theory approach
Physics of the Dark Universe, 2013
If dark matter is a new species of particle produced in the early universe as a cold thermal relic (a weakly-interacting massive particle-WIMP), its present abundance, its scattering with matter in direct-detection experiments, its present-day annihilation signature in indirect-detection experiments, and its production and detection at colliders, depend crucially on the WIMP coupling to standard-model (SM) particles. It is usually assumed that the WIMP couples to the SM sector through its interactions with quarks and leptons. In this paper we explore the possibility that the WIMP coupling to the SM sector is via electroweak gauge and Higgs bosons. In the absence of an ultraviolet-complete particle-physics model, we employ effective field theory to describe the WIMP-SM coupling. We consider both scalars and Dirac fermions as possible dark-matter candidates. Starting with an exhaustive list of operators up to dimension 8, we present detailed calculation of dark-matter annihilations to all possible final states, including γγ, γZ, γh, ZZ, Zh, W + W − , hh, and ff , and demonstrate the correlations among them. We compute the mass scale of the effective field theory necessary to obtain the correct dark-matter mass density, and well as the resulting photon line signals. PACS numbers: 98.70.Cq, 95.35.+d, 95.30.Cq, 95.55.Ka, 95.85.Ry
Lepton Mass Generation and Family Number Violation Mechanism in the SU(6) L ⊗ U(1) y Model
International Journal of Modern Physics A, 1998
Lepton family number violation processes arise in the SU(6) L⊗ U(1) Y model due to the presence of an extra neutral gauge boson, Z′, with family changing couplings, and due to the fact that this model demands the existence of heavy exotic leptons. The mixing of the standard Z with Z′ and the mixing of ordinary leptons with exotic ones induce together family changing couplings on the Z and therefore nonvanishing rates for lepton family number violation processes, such as [Formula: see text], [Formula: see text] and μ→eγ. Additional contributions to the processes μ→eγ and [Formula: see text] are induced from the mass generation mechanism. This last type of contributions may compete with the above one, depending on the masses of the scalars which participate in the diagrams which generate radiatively the masses of the charged leptons. Using the experimental data we compute some bounds for the mixings parameters and for the masses of the scalars.
Fermion dark matter and radiative neutrino masses from spontaneous lepton number breaking
New Journal of Physics, 2020
In this paper, we study the viability of having a fermion Dark Matter particle below the TeV mass scale in connection to the neutrino mass generation mechanism. The simplest realisation is achieved within the scotogenic model where neutrino masses are generated at the 1-loop level. Hence, we consider the case where the dark matter particle is the lightest Z 2 -odd Majorana fermion running in the neutrino mass loop. We assume that lepton number is broken dynamically due to a lepton number carrier scalar singlet which acquires a non-zero vacuum expectation value. In the present scenario the Dark Matter particles can annihilate via t- and s-channels. The latter arises from the mixing between the new scalar singlet and the Higgs doublet. We identify three different Dark Matter mass regions below 1 TeV that can account for the right amount of dark matter abundance in agreement with current experimental constraints. We compute the Dark Matter-nucleon spin-independent scattering cross-sect...
Physical Review D, 2014
We propose a new paradigm for generating exponentially spread standard model Yukawa couplings from a new U (1)F gauge symmetry in the dark sector. Chiral symmetry is spontaneously broken among dark fermions that obtain non-vanishing masses from a non-perturbative solution to the mass gap equation. The necessary ingredient for this mechanism to work is the existence of higher derivative terms in the dark U (1)F theory, or equivalently the existence of Lee-Wick ghosts, that (i) allow for a non-perturbative solution to the mass gap equation in the weak coupling regime of the Abelian theory; (ii) induce exponential dependence of the generated masses on dark fermion U (1)F quantum numbers. The generated flavor and chiral symmetry breaking in the dark sector is transferred to the standard model Yukawa couplings at one loop level via Higgs portal type scalar messenger fields. The latter carry quantum numbers of squarks and sleptons. A new intriguing phenomenology is predicted that could be potentially tested at the LHC, provided the characteristic mass scale of the messenger sector is accessible at the LHC as is suggested by naturalness arguments.
Scalar dark matter, neutrino mass and leptogenesis in a U(1) B−L model
Journal of Physics G: Nuclear and Particle Physics, 2021
We investigate the phenomenology of singlet scalar dark matter (DM) in a simple U(1) B−L gauge extension of the standard model, made anomaly-free with four exotic fermions. The enriched scalar sector and the new gauge boson Z′, associated with U(1) gauge extension, connect the dark sector to the visible sector. We compute relic density, consistent with Planck limit and a Z′ mediated DM-nucleon cross section, compatible with PandaX bound. The mass of Z′ and the corresponding gauge coupling are constrained from LEP-II and LHC dilepton searches. We also briefly scrutinize the tree-level neutrino mass with a dimension five operator. Furthermore, resonant leptogenesis phenomena is discussed with TeV-scale exotic fermions to produce the observed baryon asymmetry of the Universe. Further, we briefly explain the impact of flavor in leptogenesis and we also project the combined constraints on Yukawa, consistent with oscillation data and observed baryon asymmetry. Additionally, we restrict th...