971 research outputs found
On the Solution to the Polonyi Problem with No-Scale Type Supergravity
We study the solution to the Polonyi problem in the framework of no-scale
type supergravity. In such a model, Polonyi field can weigh as
and decay just before the big-bang nucleosynthesis. It is shown that in spite
of a large entropy production by the decay of the Polonyi field, one can
naturally explain the present value of the baryon-to-entropy ratio, if the Affleck-Dine mechanism for baryogenesis works. It
is pointed out, however, that there is another cosmological problem related to
the abundance of the lightest superparticles produced by the decay of the
Polonyi field.Comment: Talk given at the Yukawa International Seminar '95 in Kyoto, 21 - 26
August, 199
A Solution to the Polonyi Problem in the Minimum SUSY-GUT
We show that the Polonyi problem is solved in the minimum SUSY-GUT model in
which a self-coupling strength for a heavy Higgs , ,
is very small . It is stressed that with this small
the mass of the physical becomes m_{\Sigma} \sim
10^{12}\GEV and the unification scale is raised up to the gravitational one,
M\simeq 2\times 10^{18}\GEV. A potential problem, however, is also pointed
out in this GUT model
Electromagnetic Cascade in the Early Universe and its Application to the Big-Bang Nucleosynthesis
We investigate the electromagnetic cascade initiated by injection of very
high energy photons in the early Universe and calculate the cascade spectrum by
solving a set of Boltzmann equations numerically. In the calculation we take
account of Compton scattering off the background electrons and pair creation
off the background nucleons as well as photon-photon processes and inverse
Compton scattering. We also apply our cascade spectrum to the big bang
nucleosynthesis with photo-dissociation processes due to heavy unstable
particles and obtain the constraint on their lifetime and abundance.Comment: 21pages (compressed and uuencoded postscript file including 6
figures
Gravitino Production in the Inflationary Universe and the Effects on Big-Bang Nucleosynthesis
Gravitino production and decay in the inflationary universe are reexamined.
Assuming that the gravitino mainly decays into a photon and a photino, we
calculate the upperbound on the reheating temperature. Compared to previous
works, we have essentially improved the following two points: (i) the helicity
gravitino production cross sections are calculated by using
the full relevant terms in the supergravity lagrangian, and (ii) the high
energy photon spectrum is obtained by solving the Boltzmann equations
numerically. Photo-dissociation of the light elements (D, T, He, He)
leads to the most stringent upperbound on the reheating temperature, which is
given by (--)GeV for the gravitino mass 100GeV--1TeV. On the
other hand, requiring that the present mass density of photino should be
smaller than the critical density, we find that the reheating temperature have
to be smaller than (--)GeV for the photino mass (10--100)GeV,
irrespectively of the gravitino mass. The effect of other decay channels is
also considered
Limit on the Color-Triplet Higgs Mass in the Minimum Supersymmetric SU(5) Model
In the minimum supersymmetric SU(5) GUT, we derive the upper limit on the
mass of the color-triplet Higgs multiplets as \mhc\leq 2.4\times 10^{16}~\GEV
(90 \% C.L.) taking all possible corrections into account in a renormalization
group analysis. If the above upper limit is compared with a limit on \mhc
from the negative search for the proton decay; \mhc \geq 2.0\times
10^{16}~\GEV (in which effects of the larger top-quark mass are included), the
minimum supersymmetric SU(5) GUT is severely constrained
Upper Bound on the Gluino Mass in Supersymmetric Models with Extra Matters
We discuss the upper bound on the gluino mass in supersymmetric models with
vector-like extra matters. In order to realize the observed Higgs mass of 125
GeV, the gluino mass is bounded from above in supersymmetric models. With the
existence of the vector-like extra matters at around TeV, we show that such an
upper bound on the gluino mass is significantly reduced compared to the case of
minimal supersymmetric standard model. This is due to the fact that radiatively
generated stop masses as well the stop trilinear coupling are enhanced in the
presence of the vector-like multiplets. In a wide range of parameter space of
the model with extra matters, the gluino is required to be lighter than TeV, which is likely to be within the reach of forthcoming LHC experiment.Comment: 16 pages, 6 figures; references adde
Lepton Flavor Violations in High-Scale SUSY with Right-Handed Neutrinos
Motivated by the recent discovery of the Higgs boson at m_h = 126 GeV and
also by the non-observation of superparticles at the LHC, high-scale SUSY,
where the superparticles are as heavy as O(10) TeV, has been recently proposed.
We study lepton-flavor violations (LFVs) in the high-scale SUSY with
right-handed neutrinos. Even if the slepton masses are of O(10) TeV, the
renormalization group (RG) effects on the slepton mass-squared matrix may
induce large enough LFVs which are within the reach of future LFV experiments.
We also discuss the implication of the right-handed neutrinos on the
electroweak symmetry breaking in such a model, and show that the parameter
region with the successful electroweak symmetry breaking is enlarged by the RG
effects due to the right-handed neutrinos.Comment: 11 pages, 3 figure
The muon anomalous magnetic dipole moment in the minimal supersymmetric standard model
The muon anomalous magnetic dipole moment (MDM) is calculated in the framework of the minimal supersymmetric standard model (MSSM). In this paper, we discuss how the muon MDM depends on the parameters in MSSM in detail. We show that the contribution of the superparticle-loop becomes significant especially when \tan\beta is large. Numerically, it becomes O(10^{-8}-10^{-9}) in a wide parameter space, which is within the reach of the new Brookhaven E821 experiment
Naturalness Re-examined: Implications for Supersymmetry Searches
We discuss the origin of "focus points" in the scalar mass RGEs of the MSSM
and their implications for collider searches. We present a new exact analytic
solution to the homogeneous system of scalar mass RGEs in the MSSM for general
. This is then used to prove that the focus point for
depends only on the value of the top Yukawa coupling at the {\em weak} scale
(not its value at the GUT scale) and is independent of the bottom Yukawa
coupling.Comment: 7 pages, 2 figures, to appear in the Proceedings of PASCOS'99, Lake
Tahoe, December 10-16, 199
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