90 research outputs found
Leptogenesis with Composite Neutrinos
Models with composite singlet neutrinos can give small Majorana or Dirac
masses to the active neutrinos. The mechanism is based on the fact that
conserved chiral symmetries give massless neutrinos at the renormalizable
level. Thus, they acquire very small masses due to non-renormalizable terms. We
investigate such models in two aspects. First, we find UV completions for them
and then we investigate the possibility of giving leptogenesis. We find that
these models offer new possibilities for leptogenesis. Models with Majorana
masses can exhibit standard leptogenesis. Models with Dirac masses can provide
a realization of Dirac type leptogenesis with mass scale that can be as low as
10 TeV.Comment: 20 pages, 4 figure
Magnetic Field Transfer From A Hidden Sector
Primordial magnetic fields in the dark sector can be transferred to magnetic
fields in the visible sector due to a gauge kinetic mixing term. We show that
the transfer occurs when the evolution of magnetic fields is dominated by
dissipation due to finite electric conductivity, and does not occur at later
times if the magnetic fields evolve according to magnetohydrodynamics scaling
laws. The efficiency of the transfer is suppressed by not only the gauge
kinetic mixing coupling but also the ratio between the large electric
conductivity and the typical momentum of the magnetic fields. We find that the
transfer gives nonzero visible magnetic fields today. However, without possible
dynamo amplifications, the field transfer is not efficient enough to obtain the
intergalactic magnetic fields suggested by the gamma-ray observations, although
there are plenty of possibilities for efficient dark magnetogenesis, which are
experimentally unconstrained.Comment: 26 pages, 2 figure
Direct Detection with Dark Mediators
We introduce dark mediator Dark matter (dmDM) where the dark and visible
sectors are connected by at least one light mediator carrying the same
dark charge that stabilizes DM. is coupled to the Standard Model via an
operator , and to dark matter via a Yukawa
coupling . Direct detection is realized as
the process at tree-level
for and small Yukawa coupling, or
alternatively as a loop-induced process . We explore the direct-detection consequences of this scenario and find
that a heavy dmDM candidate fakes different
standard WIMPs in different experiments. Large
portions of the dmDM parameter space are detectable above the irreducible
neutrino background and not yet excluded by any bounds. Interestingly, for the
range leading to novel direct detection phenomenology, dmDM is also a
form of Self-Interacting Dark Matter (SIDM), which resolves inconsistencies
between dwarf galaxy observations and numerical simulations.Comment: 9 pages, 8 figures + reference
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