132 research outputs found
New model for radiatively generated Dirac neutrino masses and lepton flavor violating decays of the Higgs boson
We propose a new mechanism to explain neutrino masses with lepton number
conservation, in which the Dirac neutrino masses are generated at the two-loop
level involving a dark matter candidate. In this model, branching ratios of
lepton flavor violating decays of the Higgs boson can be much larger than those
of lepton flavor violating decays of charged leptons. If lepton flavor
violating decays of the Higgs boson are observed at future collider experiments
without detecting lepton flavor violating decays of charged leptons, most of
the models previously proposed for tiny neutrino masses are excluded while our
model can still survive. We show that the model can be viable under constraints
from current data for neutrino experiments, searches for lepton flavor
violating decays of charged leptons and dark matter experiments.Comment: 26 pages, 9 eps file
Electroweak baryogenesis in the three-loop neutrino mass model with dark matter
Baryon asymmetry of the Universe is evaluated in the model originally
proposed in Phys. Rev. Lett. 102 (2009) 051805, where Majorana masses of
neutrinos are generated via three-loop diagrams composed of additional scalar
bosons including the dark matter candidate which is odd under an unbroken
symmetry. In order for the model to include multiple CP-violating phases, we do
not impose the softly broken symmetry imposed in the original model to
avoid the flavor-changing neutral current at tree level. Instead, for
simplicity, we assume the flavor alignment structure in the Yukawa
interactions. We also simply assume the alignment structure in the Higgs
potential so that the Higgs couplings coincide with those in the SM at tree
level. Under these phenomenological simplifications, the model still contains
multiple CP-violating phases. By using destructive interferences among them, it
is compatible with the stringent constraint from the electric dipole moment
measurements to generate the observed baryon asymmetry along with the scenario
of electroweak baryogenesis. We show a benchmark scenario which can explain
neutrino mass, dark matter and baryon asymmetry of the universe simultaneously
and can satisfy all the other available experimental data. Some
phenomenological predictions of the model are also discussed.Comment: 45 pages, 4 figures, 2 tables, one figure and appendices added, fixed
typo
Revisiting Affleck-Dine Leptogenesis with light sleptons
We revisit the Affleck-Dine leptogenesis via the flat direction with
a light slepton field. Although the light slepton field is favored in
low-energy SUSY phenomenologies, such as the muon anomaly and
bino-slepton coannihilation, it may cause a problem in the Affleck-Dine
leptogenesis: it may create an unwanted charge-breaking vacuum in the
Affleck-Dine field potential so that the Affleck-Dine field is trapped during
the course of leptogenesis. We investigate the conditions under which such an
unwanted vacuum exists and clarify that both thermal and quantum corrections
are important for the (temporal) disappearance of the charge-breaking minimum.
We also confirm that if the charge-breaking vacuum disappears due to the
thermal or quantum correction, the correct baryon asymmetry can be produced
while avoiding the cosmological gravitino problem.Comment: 12 pages, 2 figures, version accepted for publication in JCAP (v2
Searching for new physics effects in future mass and determinations
We investigate the phenomenology of the dark boson, , which is
associated with a new Abelian gauge symmetry and couples to the standard model
particles via kinetic mixing and mass mixing .
We examine two cases: (i) is lighter than the boson, and (ii)
is heavier than that. In the first case, it is known that causes a
deviation in the weak mixing angle at low energies from the standard model
prediction. We study the prediction in the model and compare it with the latest
experimental data. In the second case, the - mixing enhances the
boson mass. We investigate the effect of on various electroweak
observables including the boson mass using the , , and
parameters. We point out an interesting feature: in the limit , the equation holds independently of the mass of and the
size of , while in many new physics models. We
find that the dark boson with a mass of with a
relatively large mass mixing can reproduce the CDF result within
while avoiding all other experimental constraints. Such dark bosons are
expected to be tested at future high-energy colliders.Comment: 20 pages, 9 figures, 1 table, more references and discussions are
adde
- …