46 research outputs found
Production of massive stable particles in inflaton decay
We point out that inflaton decays can be a copious source of stable or
long--lived particles with mass exceeding the reheat temperature .
Once higher order processes are included, this statement is true for any
particle with renormalizable (gauge or Yukawa) interactions. This contribution
to the density often exceeds the contribution from thermal
production, leading to significantly stronger constraints on model parameters
than those resulting from thermal production alone. For example, we all
but exclude models containing stable charged particles with mass less than half
the mass of the inflaton.Comment: 4 revtex pages, 1 figure (uses axodraw). Slightly modified for better
clarification, few changes in references. Final verssion published in Phys.
Rev. Let
Leptogenesis with Almost Degenerate Majorana Neutrinos
We investigate the leptogenesis with almost degenerate neutrinos, in the
framework of democratic mass matrix, which naturally explains the large mixing
angles for neutrino oscillations as well as quark masses and mixing matrix. We
find that the baryon asymmetry in the present universe is explained via the
decays of right-handed neutrinos produced nonthermally by the inflaton decay.
The model predicts neutrinoless double beta decays accessible in near future
experiments.Comment: 17 pages, LaTeX, 2 figure
Reheating-temperature independence of cosmological baryon asymmetry in Affleck-Dine leptogenesis
In this paper we point out that the cosmological baryon asymmetry in our
universe is generated almost independently of the reheating temperature
in Affleck-Dine leptogenesis and it is determined mainly by the mass of the
lightest neutrino, , in a wide range of the reheating temperature
-- GeV. The present baryon asymmetry predicts the
in a narrow region, -- eV.
Such a small mass of the lightest neutrino leads to a high predictability on
the mass parameter contributing to the neutrinoless double
beta decay. We also propose an explicit model in which such an ultralight
neutrino can be naturally obtained.Comment: 22 pages, LaTeX, 9 eps figure
Double Inflation in Supergravity and the Large Scale Structure
The cosmological implication of a double inflation model with hybrid + new
inflations in supergravity is studied. The hybrid inflation drives an inflaton
for new inflation close to the origin through supergravity effects and new
inflation naturally occurs. If the total e-fold number of new inflation is
smaller than , both inflations produce cosmologically relevant density
fluctuations. Both cluster abundances and galaxy distributions provide strong
constraints on the parameters in the double inflation model assuming
standard cold dark matter scenario. The future satellite
experiments to measure the angular power spectrum of the cosmic microwave
background will make a precise determination of the model parameters possible.Comment: 19 pages (RevTeX file
Leptogenesis in Inflationary Universe
We investigate the leptogenesis via decays of heavy Majorana neutrinos which
are produced non-thermally in inflaton decays. We make a comprehensive study on
the leptogenesis assuming various supersymmetric (SUSY) models for hybrid, new
and topological inflations. For an estimation of the lepton asymmetry we adopt
the Froggatt-Nielsen mechanism for mass matrices of quarks and leptons. We find
that all of these models are successful to produce the lepton asymmetry enough
to explain the baryon number in the present universe. Here we impose low
reheating temperatures such as GeV in order to suppress the
abundance of gravitinos not to conflict with the big-bang nucleosynthesis.
Furthermore, we find that the leptogenesis works very well even with GeV in the SUSY hybrid or new inflation model. It is known that
such a reheating temperature is low enough to suppress the abundance of
gravitinos of mass GeV--1 TeV. Thus, the leptogenesis is
fully consistent with the big-bang nucleosynthesis in a wide region of the
gravitino mass.Comment: 42 pages, 17 figure
Non-thermal leptogenesis with almost degenerate superheavy neutrinos
We present a model with minimal assumptions for non-thermal leptogenesis with
almost degenerate superheavy right-handed neutrinos in a supersymmetric set up.
In this scenario a gauge singlet inflaton is directly coupled to the
right-handed (s)neutrinos with a mass heavier than the inflaton mass. This
helps avoiding potential problems which can naturally arise otherwise. The
inflaton decay to the Standard Model leptons and Higgs, via off-shell
right-handed (s)neutrinos, reheats the Universe. The same channel is also
responsible for generating the lepton asymmetry, thus requiring no stage of
preheating in order to excite superheavy (s)neutrinos. The suppressed decay
rate of the inflaton naturally leads to a sufficiently low reheat temperature,
which in addition, prevents any wash out of the yielded asymmetry. We will
particularly elaborate on important differences from leptogenesis with on-shell
(s)neutrinos. It is shown that for nearly degenerate neutrinos a successful
leptogenesis can be accommodated for a variety of inflationary models with a
rather wide ranging inflationary scale.Comment: 10 revtex pages, 2 figure (uses axodraw). The derivation of the
asymmetry parameter for the general case and one figure added. Final version
to appear in Phys. Rev.
Natural Chaotic Inflation in Supergravity and Leptogenesis
We comprehensively investigate a chaotic inflation model proposed recently in
the framework of supergravity. In this model, the form of K\"ahler potential is
determined by a symmetry, that is, the Nambu-Goldstone-like shift symmetry,
which guarantees the absence of the exponential factor in the potential for the
inflaton field. Though we need the introduction of small parameters, the
smallness of the parameters is justified also by symmetries. That is, the zero
limit of the small parameters recovers symmetries, which is natural in the 't
Hooft's sense. The leptogenesis scenario via the inflaton decay in this chaotic
inflation model is also discussed. We find that the lepton asymmetry enough to
explain the present baryon number density is produced for low reheating
temperatures avoiding the overproduction of gravitinos.Comment: 16 pages. To appear in Phys. Rev.
Leptogenesis and Neutrino Oscillations Within A Predictive G(224)/SO(10)-Framework
A framework based on an effective symmetry that is either G(224)= SU(2)_L x
SU(2)_R xSU(4)^c or SO(10) has been proposed (a few years ago) that
successfully describes the masses and mixings of all fermions including
neutrinos, with seven predictions, in good accord with the data. Baryogenesis
via leptogenesis is considered within this framework by allowing for natural
phases (~ 1/20-1/2) in the entries of the Dirac and Majorana mass-matrices. It
is shown that the framework leads quite naturally, for both thermal as well as
non-thermal leptogenesis, to the desired magnitude for the baryon asymmetry.
This result is obtained in full accord with the observed features of the
atmospheric and solar neutrino oscillations, as well as with those of the quark
and charged lepton masses and mixings, and the gravitino-constraint. Hereby one
obtains a unified description of fermion masses, neutrino oscillations and
baryogenesis (via leptogenesis) within a single predictive framework.Comment: Efficiency factor updated, some clarifications and new references
added. 19 page
Hidden SUSY at the LHC: the light higgsino-world scenario and the role of a lepton collider
While the SUSY flavor, CP and gravitino problems seem to favor a very heavy
spectrum of matter scalars, fine-tuning in the electroweak sector prefers low
values of superpotential mass \mu. In the limit of low \mu, the two lightest
neutralinos and light chargino are higgsino-like. The light charginos and
neutralinos may have large production cross sections at LHC, but since they are
nearly mass degenerate, there is only small energy release in three-body
sparticle decays. Possible dilepton and trilepton signatures are difficult to
observe after mild cuts due to the very soft p_T spectrum of the final state
isolated leptons. Thus, the higgsino-world scenario can easily elude standard
SUSY searches at the LHC. It should motivate experimental searches to focus on
dimuon and trimuon production at the very lowest p_T(\mu) values possible. If
the neutralino relic abundance is enhanced via non-standard cosmological dark
matter production, then there exist excellent prospects for direct or indirect
detection of higgsino-like WIMPs. While the higgsino-world scenario may easily
hide from LHC SUSY searches, a linear e^+e^- collider or a muon collider
operating in the \sqrt{s}\sim 0.5-1 TeV range would be able to easily access
the chargino and neutralino pair production reactions.Comment: 20 pages including 12 .eps figure
Neutralino Dark Matter from MSSM Flat Directions in light of WMAP Result
The minimal supersymmetric standard model (MSSM) has a truly supersymmetric
way to explain both the baryon asymmetry and cold dark matter in the present
Universe, that is, ``Affleck-Dine baryo/DM-genesis.'' The associated late-time
decay of Q-balls directly connects the origins of the baryon asymmetry and dark
matter, and also predicts a specific nature of the LSP. In this paper, we
investigate the prospects for indirect detection of these dark matter
candidates observing high energy neutrino flux from the Sun, and hard positron
flux from the halo. We also update the previous analysis of the direct
detection in hep-ph/0205044 by implementing the recent result from WMAP
satellite.Comment: 32 pages, including 40 figure