40 research outputs found
Leptogenesis Scenarios via Non-Thermally Produced Right-handed Neutrino and Sneutrino in Supersymmetric Seesaw Model
We reconsidered leptogenesis scenario from right-handed (s)neutrino produced
by the decay of inflaton. Besides the well-investigated case that the neutrino
decays instantaneously after the production, leptogenesis is possible if
neutrino decays after it dominates the universe. In the latter case,
right-handed (s)neutrino can decay either while it is relativistic or after it
becomes non-relativistic. Especially, the first case has not been discussed
seriously in literatures. Resultant lepton asymmetry and constraints from the
gravitino problem are studied in broad parameter region, including all cases of
this scenario. It is also shown how this leptogenesis scenario depends on the
parameters, the inflaton decay rate (the reheating temperature), the
right-handed neutrino mass, the washout parameter, and the constraint from the
gravitino problem. Leptogenesis from relativistic neutrino decay is interesting
because both thermal and non-thermal gravitino problems can be relaxed.Comment: 17 pages, 6 figure
Light Higgs boson scenario in the SUSY seesaw model
It is demonstrated that the light Higgs boson scenario, which the lightest
Higgs mass is less than the LEP bound, mh > 114.4 GeV, is consistent with the
SUSY seesaw model. With the assumptions of the universal right-handed neutrino
mass and the hierarchical mass spectrum of the ordinary neutrinos, the bounds
for the right-handed neutrino mass is investigated in terms of lepton flavor
violating charged lepton decays. We also discuss the effect of the modification
of renormalization group equations by the right-handed neutrinos on the b to s
gamma process and the relic abundance of dark matter in the light Higgs boson
scenario.Comment: 17 pages, 5 figure
Affleck-Dine leptogenesis via multiscalar evolution in a supersymmetric seesaw model
A leptogenesis scenario in a supersymmetric standard model extended with
introducing right-handed neutrinos is reconsidered. Lepton asymmetry is
produced in the condensate of a right-handed sneutrino via the Affleck-Dine
mechanism. The LH_u direction develops large value due to a negative effective
mass induced by the right-handed sneutrino condensate through the Yukawa
coupling of the right-handed neutrino, even if the minimum during the inflation
is fixed at the origin. The lepton asymmetry is nonperturbatively transfered to
the LH_u direction by this Yukawa coupling.Comment: 19 pages, 3 figures. Revised version for publication. The model was
modified to fix some problem
Leptogenesis via multiscalar coherent evolution with supersymmetric neutrino see-saw
A novel scenario of leptogenesis is investigated in the supersymmetric
neutrino see-saw model. The right-handed sneutrino and the field in the direction of the slepton and Higgs
doublets start together coherent evolution after the inflation with
right-handed neutrino mass smaller than the Hubble parameter of
inflation. Then, after some period the motion of and is
drastically changed by the cross coupling
from the and terms, and the significant
asymmetries of and are generated. The asymmetry is fixed later by the thermal effect as the lepton number
asymmetry for baryogenesis, while the asymmetry disappears
through the decays with almost the same rate but opposite final lepton numbers.Comment: 4pages, 1 figure; submitted to Physical Review D. The renormalization
group effects were include
Spinless photon dark matter from two universal extra dimensions
We explore the properties of dark matter in theories with two universal extra
dimensions, where the lightest Kaluza-Klein state is a spin-0 neutral particle,
representing a six-dimensional photon polarized along the extra dimensions.
Annihilation of this 'spinless photon' proceeds predominantly through Higgs
boson exchange, and is largely independent of other Kaluza-Klein particles. The
measured relic abundance sets an upper limit on the spinless photon mass of 500
GeV, which decreases to almost 200 GeV if the Higgs boson is light. The
phenomenology of this dark matter candidate is strikingly different from
Kaluza-Klein dark matter in theories with one universal extra dimension.
Elastic scattering of the spinless photon with quarks is helicity suppressed,
making its direct detection challenging, although possible at upcoming
experiments. The prospects for indirect detection with gamma rays and
antimatter are similar to those of neutralinos. The rates predicted at neutrino
telescopes are below the sensitivity of next-generation experiments.Comment: 22 pages. Figure 7 corrected, leading to improved prospects for
direct detection. Some clarifying remarks include
Affleck-Dine baryogenesis with modulated reheating
Modulated reheating scenario is one of the most attractive models that
predict possible detections of not only the primordial non-Gaussianity but also
the tensor fluctuation through future CMB observations such as the Planck
satellite, the PolarBeaR and the LiteBIRD satellite experiments. We study the
baryonic-isocurvature fluctuations in the Affleck-Dine baryogenesis with the
modulated reheating scenario. We show that the Affleck-Dine baryogenesis can be
consistent with the modulated reheating scenario with respect to the current
observational constraint on the baryonic-isocurvature fluctuations.Comment: 7 page
Flavour Issues in Leptogenesis
We study the impact of flavour in thermal leptogenesis, including the quantum
oscillations of the asymmetries in lepton flavour space. In the Boltzmann
equations we find different numerical factors and additional terms which can
affect the results significantly. The upper bound on the CP asymmetry in a
specific flavour is weaker than the bound on the sum. This suggests that --
when flavour dynamics is included -- there is no model-independent limit on the
light neutrino mass scale,and that the lower bound on the reheat temperature is
relaxed by a factor ~ (3 - 10).Comment: 19 pages, corrected equations for flavour oscillation
Leptogenesis from a sneutrino condensate revisited
We re--examine leptogenesis from a right--handed sneutrino condensate, paying
special attention to the term associated with the see--saw Majorana mass.
This term generates a lepton asymmetry in the condensate whose time average
vanishes. However, a net asymmetry will result if the sneutrino lifetime is not
much longer than the period of oscillations. Supersymmetry breaking by thermal
effects then yields a lepton asymmetry in the standard model sector after the
condensate decays. We explore different possibilities by taking account of both
the low--energy and Hubble terms. It will be shown that the desired baryon
asymmetry of the Universe can be obtained for a wide range of Majorana mass.Comment: 17 revtex pages, 3 figures, 1 table. Slightly modified and references
added. Final version accepted for publication in Phys. Rev.
Low energy antideuterons: shedding light on dark matter
Low energy antideuterons suffer a very low secondary and tertiary
astrophysical background, while they can be abundantly synthesized in dark
matter pair annihilations, therefore providing a privileged indirect dark
matter detection technique. The recent publication of the first upper limit on
the low energy antideuteron flux by the BESS collaboration, a new evaluation of
the standard astrophysical background, and remarkable progresses in the
development of a dedicated experiment, GAPS, motivate a new and accurate
analysis of the antideuteron flux expected in particle dark matter models. To
this extent, we consider here supersymmetric, universal extra-dimensions (UED)
Kaluza-Klein and warped extra-dimensional dark matter models, and assess both
the prospects for antideuteron detection as well as the various related sources
of uncertainties. The GAPS experiment, even in a preliminary balloon-borne
setup, will explore many supersymmetric configurations, and, eventually, in its
final space-borne configuration, will be sensitive to primary antideuterons
over the whole cosmologically allowed UED parameter space, providing a search
technique which is highly complementary with other direct and indirect dark
matter detection experiments.Comment: 26 pages, 7 figures; version to appear in JCA