317 research outputs found
Hadronic Axion Model in Gauge-Mediated Supersymmetry Breaking
A simple hadronic axion model is proposed in the framework of gauge-mediated
supersymmetry breaking. Dynamics of Peccei-Quinn symmetry breaking is governed
by supersymmetry breaking effects and the Peccei-Quinn breaking scale
is inversely proportional to the gravitino mass. The gravitino mass range which
corresponds to the axion window GeV -- GeV
lies in the region predicted by gauge-mediated supersymmetry breaking models.
The model is also shown to be cosmologically viable.Comment: 20 pages including seven postscript figures, reviced version to be
published in Physics Letters
Gravitinos from Heavy Scalar Decay
Cosmological issues of the gravitino production by the decay of a heavy
scalar field are examined, assuming that the damped coherent oscillation of
the scalar once dominates the energy of the universe. The coupling of the
scalar field to a gravitino pair is estimated both in spontaneous and explicit
supersymmetry breaking scenarios, with the result that it is proportional to
the vacuum expectation value of the scalar field in general. Cosmological
constraints depend on whether the gravitino is stable or not, and we study each
case separately. For the unstable gravitino with 100GeV--10TeV,
we obtain not only the upper bound, but also the lower bound on the reheating
temperature after the decay, in order to retain the success of the big-bang
nucleosynthesis. It is also shown that it severely constrains the decay rate
into the gravitino pair. For the stable gravitino, similar but less stringent
bounds are obtained to escape the overclosure by the gravitinos produced at the
decay. The requirement that the free-streaming effect of such gravitinos
should not suppress the cosmic structures at small scales eliminates some
regions in the parameter space, but still leaves a new window of the gravitino
warm dark matter. Implications of these results to inflation models are
discussed. In particular, it is shown that modular inflation will face serious
cosmological difficulty when the gravitino is unstable, whereas it can escape
the constraints for the stable gravitino. A similar argument offers a solution
to the cosmological moduli problem, in which the moduli is relatively heavy
while the gravitino is light.Comment: 14 pages, 8 figure
HCV Virus and Lymphoid Neoplasms
Hepatitis C virus (HCV) is one of the viruses known to cause hepatic cancer. HCV is also believed to be involved in malignant lymphoma. In this paper, we investigated characteristics of malignant lymphoma cases that were anti-HCV antibody (HCV-Ab) positive. We were able to perform pathological examinations on 13 out of 14 HCV-positive cases. Of these, lymphoid tissues of 10 stained positive for HCV-Ab. There was no significant correlation between the degree of HCV staining and the rate of recurrence or resistance to treatment. However, there did appear to be a consistent decrease in the amount of HCV-RNA between pre- and posttreatment among HCV-Ab-positive cases; that is, treatment-resistant cases that exhibited resistance from the first treatment and recurrent cases more frequently had a higher HCV level at treatment termination compared to the pretreatment level. This suggests that the HCV virus either accelerates oncogenesis by direct interaction with B cells or indirectly affects lymphoma prognosis
Rituximab Administration and Reactivation of HBV
Rituximab is a drug used for the treatment of B-cell non-Hodgkin's lymphoma, and its range of use has expanded to the treatment of collagen diseases such as idiopathic thrombocytopenic purpura and rheumatoid arthritis. One serious complication of rituximab use is the reactivation of dormant hepatitis B virus, and prevention of this phenomenon has become an urgent issue. This paper provides a general outline of the problem through an analysis of patient cases that we and other groups have experienced to date
Late-time entropy production due to the decay of domain walls
It is shown that late-time decay of domain walls can dilute unwanted relics
such as moduli, if the universe was dominated by frustrated domain walls with
tension . Since energy density of the frustrated
domain walls decreases as slow as the inverse of the scale factor, an
overclosure limit on the axion decay constant is also considerably
relaxed. In fact can be as large as the Planck scale, which may enable us
to naturally implement the QCD axion in the string scheme. Furthermore, in
contrast to thermal inflation models, the Affleck-Dine baryogenesis can
generate enough asymmetry to explain the present baryon abundance, even in the
presence of late-time entropy production.Comment: 5 pages, no figure; a few explanatory comments are added, conclusion
unchange
Hubble Induced Mass in Radiation Dominated Universe
We reconsider the effective mass of a scalar field which interact with
visible sector via Planck-suppressed coupling in supergravity framework. We
focus on the radiation-dominated (RD) era after inflation. In this era, the
effective mass is given by thermal average of interaction terms. To make our
analysis clear, we rely on Kadanoff-Baym equations to evaluate the thermal
average. We find that, in RD era, a scalar field acquires the effective mass of
the order of .Comment: 10 pages, v2:minor corrections and a reference added, v3:a footnote
added, version accepted by PL
Right-handed sneutrino dark matter and big-bang nucleosynthesis
We study the light-element abundances in supersymmetric model where the
right-handed sneutrino is the lightest superparticle (LSP), assuming that the
neutrino masses are purely Dirac-type. In such a scenario, the lightest
superparticle in the minimal supersymmetric standard model sector (which we
call MSSM-LSP) becomes long-lived, and thermal relic MSSM-LSP may decay after
the big-bang nucleosynthesis starts. We calculate the light-element abundances
including non-standard nuclear reactions induced by the MSSM-LSP decay, and
derive constraints on the scenario of right-handed sneutrino LSP.Comment: 13 pages, 4 figure
Hadronic Axion Model in Gauge-Mediated Supersymmetry Breaking and Cosmology of Saxion
Recently we have proposed a simple hadronic axion model within gauge-mediated
supersymmetry breaking. In this paper we discuss various cosmological
consequences of the model in great detail. A particular attention is paid to a
saxion, a scalar partner of an axion, which is produced as a coherent
oscillation in the early universe. We show that our model is cosmologically
viable, if the reheating temperature of inflation is sufficiently low. We also
discuss the late decay of the saxion which gives a preferable power spectrum of
the density fluctuation in the standard cold dark matter model when compared
with the observation.Comment: 24 pages, 3 figure
Anomaly-Mediated Supersymmetry Breaking with Axion
We construct hadronic axion models in the framework of the anomaly-mediated
supersymmetry breaking scenario. If the Peccei-Quinn symmetry breaking is
related to the supersymmetry breaking, mass spectrum of the minimal
anomaly-mediated scenario is modified, which may solve the negative slepton
mass problem in the minimal anomaly-mediated model. We find several classes of
phenomenologically viable models of axion within the framework of the anomaly
mediation and, in particular, we point out a new mechanism of stabilizing the
axion potential. In this class of models, the Peccei-Quinn scale is related to
the messenger scale. We also study phenomenological aspects of this class of
models. We will see that, in some case, the lightest particle among the
superpartners of the standard-model particles is stau while the lightest
superparticle becomes the axino, the superpartner of the axion. With such a
unique mass spectrum, conventional studies of the collider physics and
cosmology for supersymmetric models should be altered.Comment: 20 pages, 5 figures, added footnotes and references for section
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