39 research outputs found
Long life stau in the minimal supersymmetric standard model
We study the stau lifetime in a scenario with the LSP taken to be a
neutralino and the NLSP being a stau, based on the minimal supersymmetric
Standard Model. The mass difference between the LSP and NLSP, , must
satisfy a few % or less for coannihilation to
occur, where is the neutralino mass. We calculate the stau
lifetime from the decay modes ,
, and and
discuss its dependence on various parameters. We find that the lifetime is in
the range -- sec for GeV. We
also discuss the connection with lepton flavor violation if there is mixing
between sleptons.Comment: 15 pages, 5 figure
Stau relic density at the Big-Bang nucleosynthesis era consistent with the abundance of the light element nuclei in the coannihilation scenario
We calculate the relic density of stau at the beginning of the Big-Bang
Nucleosynthesis (BBN) era in the coannihilation scenario of minimal
supersymmetric standard model (MSSM). In this scenario, stau can be long-lived
and form bound states with nuclei. We put constraints on the parameter space of
MSSM by connecting the calculation of the relic density of stau to the
observation of the light elements abundance, which strongly depends on the
relic density of stau. Consistency between the theoretical prediction and the
observational result, both of the dark matter abundance and the light elements
abundance, requires the mass difference between the lighter stau and the
lightest neutralino to be around 100MeV, the stau mass to be 300 -- 400 GeV,
and the mixing angle of the left and right-handed staus to be
.Comment: 9 pages, 5 figures, figure 5 correcte
Possible solution to the Li problem by the long lived stau
Modification of standard big-bang nucleosynthesis is considered in the
minimal supersymmetric standard model to resolve the excessive theoretical
prediction of the abundance of primordial lithium 7. We focus on the stau as a
next-lightest superparticle, which is long lived due to its small mass
difference with the lightest superparticle. It provides a number of additional
decay processes of and . A particularly
important process is the internal conversion in the stau-nucleus bound state,
which destroys the and effectively. We show
that the modification can lead to a prediction consistent with the observed
abundance of .Comment: 6 pages, 5 figure
Big-bang nucleosynthesis with a long-lived charged massive particle including He spallation processes
We propose helium-4 spallation processes induced by long-lived stau in
supersymmetric standard models, and investigate an impact of the processes on
light elements abundances. We show that, as long as the phase space of helium-4
spallation processes is open, they are more important than stau-catalyzed
fusion and hence constrain the stau property.Comment: 12 pages, 4 figures, 1 table, references added, all figures correcte
Model building by coset space dimensional reduction in ten-dimensions with direct product gauge symmetry
We investigate ten-dimensional gauge theories whose extra six-dimensional
space is a compact coset space, , and gauge group is a direct product of
two Lie groups. We list up candidates of the gauge group and embeddings of
into them. After dimensional reduction of the coset space,we find fermion and
scalar representations of with
and which accomodate all of the standard
model particles. We also discuss possibilities to generate distinct Yukawa
couplings among the generations using representations with a different
dimension for and models.Comment: 14 pages; added local report number, added refferenc
Amplification of non-Markovian decay due to bound state absorption into continuum
It is known that quantum systems yield non-exponential (power law) decay on
long time scales, associated with continuum threshold effects contributing to
the survival probability for a prepared initial state. For an open quantum
system consisting of a discrete state coupled to continuum, we study the case
in which a discrete bound state of the full Hamiltonian approaches the energy
continuum as the system parameters are varied. We find in this case that at
least two regions exist yielding qualitatively different power law decay
behaviors; we term these the long time `near zone' and long time `far zone.' In
the near zone the survival probability falls off according to a power
law, and in the far zone it falls off as . We show that the timescale
separating these two regions is inversely related to the gap between the
discrete bound state energy and the continuum threshold. In the case that the
bound state is absorbed into the continuum and vanishes, then the time scale
diverges and the survival probability follows the power law even
on asymptotic scales. Conversely, one could study the case of an anti-bound
state approaching the threshold before being ejected from the continuum to form
a bound state. Again the power law dominates precisely at the point of
ejection.Comment: 15 pages, 9 figure
Nonexponential decay of an unstable quantum system: Small--value s-wave decay
We study the decay process of an unstable quantum system, especially the
deviation from the exponential decay law. We show that the exponential period
no longer exists in the case of the s-wave decay with small value, where
the value is the difference between the energy of the initially prepared
state and the minimum energy of the continuous eigenstates in the system. We
also derive the quantitative condition that this kind of decay process takes
place and discuss what kind of system is suitable to observe the decay.Comment: 17 pages, 6 figure
Implications of Catalyzed BBN in the CMSSM with Gravitino Dark Matter
We investigate gravitino dark matter scenarios in which the primordial ^6Li
production is catalyzed by bound-state formation of long-lived negatively
charged particles X^- with ^4He. In the constrained minimal supersymmetric
Standard Model (CMSSM) with the stau^- as the X^-, the observationally inferred
bound on the primordial ^6Li abundance allows us to derive a rigid lower limit
on the gaugino mass parameter for a standard cosmological history. This limit
can have severe implications for supersymmetry searches at the Large Hadron
Collider and for the reheating temperature after inflation.Comment: 4 pages, 2 figures; note and paragraph added; references updated
Solution to Big-Bang Nucleosynthesis in Hybrid Axion Dark Matter Model
Following a recent suggestion of axion cooling of photons between the
nucleosynthesis and recombination epochs in the Early Universe, we investigate
a hybrid model with both axions and relic supersymmetric particles. In this
model we demonstrate that the 7Li abundance can be consistent with observations
without destroying the important concordance of deuterium abundance.Comment: 5 pages, 3 figure
Standard(-like) Model from an SO(12) Grand Unified Theory in six-dimensions with extra-space
We analyze a gauge-Higgs unification model which is based on a gauge theory
defined on a six-dimensional spacetime with an extra-space. We impose a
symmetry condition for a gauge field and non-trivial boundary conditions of the
. We provide the scheme for constructing a four-dimensional theory from
the six-dimensional gauge theory under these conditions. We then construct a
concrete model based on an SO(12) gauge theory with fermions which lie in a 32
representation of SO(12), under the scheme. This model leads to a
Standard-Model(-like) gauge theory which has gauge symmetry SU(3)
SU(2) U(1)( U(1)) and one generation of SM
fermions, in four-dimensions. The Higgs sector of the model is also analyzed,
and it is shown that the electroweak symmetry breaking and the prediction of
W-boson and Higgs-boson masses are obtained.Comment: 18 page