12,635 research outputs found
From Dirac neutrino masses to baryonic and dark matter asymmetries
We consider an SU(3)'_c\times SU(2)'_L\times U(1)'_Y dark sector, parallel to
the SU(3)_c\times SU(2)_L\times U(1)_Y ordinary sector. The hypercharges,
baryon numbers and lepton numbers in the dark sector are opposite to those in
the ordinary sector. We further introduce three types of messenger sectors: (i)
two or more gauge-singlet Dirac fermions, (ii) two or more [SU(2)_L\times
SU(2)'_L]-bidoublet Higgs scalars, (iii) at least one gauge-singlet Dirac
fermion and at least one [SU(2)_L\times SU(2)'_L]-bidoublet Higgs scalar. The
lepton number conserving decays of the heavy fermion singlet(s) and/or Higgs
bidoublet(s) can simultaneously generate a lepton asymmetry in the
[SU(2)_L]-doublet leptons and an opposite lepton asymmetry in the
[SU(2)'_L]-doublet leptons to account for the cosmological baryon asymmetry and
dark matter relic density, respectively. The lightest dark nucleon as the dark
matter particle should have a mass about 5 GeV. By integrating out the heavy
fermion singlet(s) and/or Higgs bidoublet(s), we can obtain three light Dirac
neutrinos composed of the ordinary and dark neutrinos. If a mirror discrete
symmetry is further imposed, our models will not require more unknown
parameters than the traditional type-I, type-II or type-I+II seesaw models.Comment: 15 pages, 6 figures. More discussions and references. To appear in
NP
High-scale leptogenesis with three-loop neutrino mass generation and dark matter
We demonstrate a common origin for high-scale leptogenesis and three-loop
neutrino mass generation. Specifically we extend the standard model by two real
singlet scalars, two singly charged scalars carrying different lepton numbers
and two or more singlet fermions with Majorana masses. Our model respects a
softly broken lepton number and an exactly conserved discrete
symmetry. Through the lepton-number-violating decays of the real scalars and
then the lepton-number-conserving decays of the charged scalars, we can obtain
a lepton asymmetry stored in the standard model leptons. This lepton asymmetry
can be partially converted to a baryon asymmetry by the sphaleron processes.
The interactions for this leptogenesis can also result in a three-loop diagram
to generate the neutrino masses. The lightest singlet fermion can keep stable
to serve as a dark matter particle.Comment: 4 pages, 2 figure
A Left-Right Symmetric Model for Neutrino Masses, Baryon Asymmetry and Dark Matter
In the left-right symmetric models without bi-doublet Higgs scalars, the
standard model fermions can obtain masses by integrating out heavy charged
singlet fermions. We find the decays of heavy neutral singlet fermions,
responsible for generating small neutrino masses, can simultaneously produce a
left-handed lepton asymmetry for baryon asymmetry and a relic density of
right-handed neutrinos for dark matter. Benefited from the left-right symmetry,
the properties of the dark matter can be related to the generation of the
neutrino masses and the baryon asymmetry. We also indicate that the decays of
the non-thermally produced right-handed neutrinos can explain the observed
fluxes of 511 keV photons from the Galactic bulge.Comment: 6 pages. Title changed. Minor corrections. To appear in PR
Mirror left-right symmetry
We propose a novel SU(3)_c\times SU(2)_L\times SU(2)_R\times U(1)_{B-L}
left-right symmetric model where the standard model fermion and Higgs fields
are SU(2)_L doublets or SU(2) singlets while their mirror partners are SU(2)_R
doublets or SU(2) singlets. The scalar fields also include a real singlet for
dark matter and two SU(2) triplets for seesaw. The mixing between the standard
model and mirror fermions is forbidden by a Z_2\times Z'_2 discrete symmetry.
The mirror charged fermions can decay into their standard model partners with
the dark-matter scalar while the mirror neutrinos can decay into the mirror
charged fermions through the right-handed gauge interactions. Our model can
have new implications on the strong CP problem, leptogenesis, collider
phenomenology and dark matter detection.Comment: 6 pages, 3 figures. One figure and some references are adde
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