80 research outputs found
A Simple Testable Model of Baryon Number Violation: Baryogenesis, Dark Matter, Neutron-Antineutron Oscillation and Collider Signals
We study a simple TeV-scale model of baryon number violation which explains
the observed proximity of the dark matter and baryon abundances. The model has
constraints arising from both low and high-energy processes, and in particular,
predicts a sizable rate for the neutron-antineutron () oscillation
at low energy and the monojet signal at the LHC. We find an interesting
complementarity among the constraints arising from the observed baryon
asymmetry, ratio of dark matter and baryon abundances, oscillation
lifetime and the LHC monojet signal. There are regions in the parameter space
where the oscillation lifetime is found to be more constraining
than the LHC constraints, which illustrates the importance of the
next-generation oscillation experiments.Comment: 8 pages, 4 figures; minor changes, version to appear in Phys. Lett.
Dark matter indirect detection signals and the nature of neutrinos in the supersymmetric extension of the standard model
In this paper, we study the prospects for determining the nature of neutrinos
in the context of a supersymmetric extension of the standard model by
using dark matter indirect detection signals and bounds on
from the cosmic microwave background data. The model contains two new dark
matter candidates whose dominant annihilation channels produce more neutrinos
than neutralino dark matter in the minimal supersymmetric standard model. The
photon and neutrino counts may then be used to discriminate between the two
models. If the dark matter comes from the B-L sector, its indirect signals and
impact on the cosmic microwave background can shed light on the nature of the
neutrinos. When the light neutrinos are of Majorana type, the indirect neutrino
signal from the Sun and the galactic center may show a prompt neutrino
box-feature, as well as an earlier cut-off in both neutrino and gamma ray
energy spectra. When the light neutrinos are of Dirac type, their contribution
to the effective number of neutrinos is at a detectable level.Comment: 11 pages, 3 figures, 2 table
Dark Matter from Late Invisible Decays to/of Gravitinos
In this work, we sift a simple supersymmetric framework of late invisible
decays to/of the gravitino. We investigate two cases where the gravitino is the
lightest supersymmetric particle or the next-to-lightest supersymmetric
particle. The next-to-lightest supersymmetric particle decays into two dark
matter candidates and has a long lifetime due to gravitationally suppressed
interactions. However, because of the absence of any hadronic or
electromagnetic products, it satisfies the tight bounds set by big bang
nucleosynthesis and cosmic microwaved background. One or both of the dark
matter candidates produced in invisible decays can contribute to the amount of
dark radiation and suppress perturbations at scales that are being probed by
the galaxy power spectrum and the Lyman-alpha forest data. We show that these
constraints are satisfied in large regions of the parameter space and, as a
result, the late invisible decays to/of the gravitino can be responsible for
the entire dark matter relic abundance.Comment: 9 pages, 6 figures. Submitted to PR
Extragalactic and galactic gamma-rays and neutrinos from annihilating dark matter
We describe cosmic gamma-ray and neutrino signals of dark matter
annihilation, explaining how the complementarity of these signals provides
additional information that, if observable, can enlighten the particle nature
of dark matter. This is discussed in the context of exploiting the separate
galactic and extragalactic components of the signal, using the spherical halo
model distribution of dark matter. We motivate the discussion with
supersymmetric extensions of the standard model of particle physics. We
consider the minimal supersymmetric standard model (MSSM) where both neutrinos
and gamma-rays are produced from annihilations. We also consider a gauged B-L,
baryon number minus lepton number, extension of the MSSM, where annihilation
can be purely to heavy right-handed neutrinos. We compare the galactic and
extragalactic components of these signals, and conclude that it is not yet
clear which may dominate when looking out of the galactic plane. To answer this
question, we must have an understanding of the contribution of halo
substructure to the annihilation signals. We find that different theories with
indistinguishable gamma-ray signals can be distinguished in the neutrino
signal. Gamma-ray annihilation signals are difficult to observe from the
galactic center, due to abundant astrophysical sources; but annihilation
neutrinos from there would not be so hidden, if they can be observed over the
atmospheric neutrinos produced by cosmic rays.Comment: 15 pages, 11 figure
Response of an Arch Dam to Non-Uniform Excitation Generated by a Seismic Wave Scattering Model
Non-uniform ground motions are generated based on a single record available at a site and seismic wave scattering analysis. The Chino Hills 2008 earthquake records at the Pacoima Dam site are used to indicate the accuracy of the method. Dynamic analysis of the Pacoima dam-reservoir-foundation under uniform and non-uniform ground motions is carried out using the EACD-3D2008 software, and the results are compared to recorded responses at different locations on the dam. There is good agreement between computed and recorded displacements of the dam for non-uniform excitation. For uniform excitation, the displacements are underestimated in comparison with those obtained from recorded excitation. Significant intensification of stresses, especially near the foundation, and different patterns of stress distribution are observed for non-uniform excitation in comparison with uniform excitation. For uniform excitation maximum stresses occur in the crown cantilever near the crest, but for non-uniform excitation the maximum stresses occur along the sides and near the foundation
Lepton Flavor Violation at the Large Hadron Collider
We investigate a potential of discovering lepton flavor violation (LFV) at
the Large Hadron Collider. A sizeable LFV in low energy supersymmetry can be
induced by massive right-handed neutrinos, which can explain neutrino
oscillations via the seesaw mechanism. We investigate a scenario where the
distribution of an invariant mass of two hadronically decaying taus
(\tauh\tauh) from \schizero{2} decays is the same in events with or without
LFV. We first develop a transfer function using this ditau mass distribution to
model the shape of the non-LFV \tauh\mu invariant mass. We then show the
feasibility of extracting the LFV \tauh\mu signal. The proposed technique can
also be applied for a LFV \tauh e search.Comment: 8 pages, 6 figures, accepted for publiucation in PR
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
Longevity of supersymmetric flat directions
We examine the fate of supersymmetric flat directions. We argue that the
non-perturbative decay of the flat direction via preheating is an unlikely
event. In order to address this issue, first we identify the physical degrees
of freedom and their masses in presence of a large flat direction VEV (Vacuum
Expectation Value). We explicitly show that the (complex) flat direction and
its fermionic partner are the only light {\it physical} fields in the spectrum.
If the flat direction VEV is much larger than the weak scale, and it has a
rotational motion, there will be no resonant particle production at all. The
case of multiple flat directions is more involved. We illustrate that in many
cases of physical interest, the situation becomes effectively the same as that
of a single flat direction, or collection of independent single directions. In
such cases preheating is not relevant. In an absence of a fast non-perturbative
decay, the flat direction survives long enough to affect thermalization in
supersymmetric models as described in hep-ph/0505050 and hep-ph/0512227. It can
also ``terminate'' an early stage of non-perturbative inflaton decay as
discussed in hep-ph/0603244.Comment: 9 revtex pages, v3: expanded discussion on two flat directions, minor
modifications, conclusions unchange
Identifying the curvaton within MSSM
We consider inflaton couplings to MSSM flat directions and the thermalization
of the inflaton decay products, taking into account gauge symmetry breaking due
to flat direction condensates. We then search for a suitable curvaton candidate
among the flat directions, requiring an early thermally induced start for the
flat direction oscillations to facilitate the necessary curvaton energy density
dominance. We demonstrate that the supersymmetry breaking -term is crucial
for achieving a successful curvaton scenario. Among the many possible
candidates, we identify the flat direction as a viable MSSM
curvaton.Comment: 9 pages. Discussion on the evaporation of condensate added, final
version published in JCA
Criticality and oscillatory behavior in non-Markovian Contact Process
A Non-Markovian generalization of one-dimensional Contact Process (CP) is
being introduced in which every particle has an age and will be annihilated at
its maximum age . There is an absorbing state phase transition which is
controlled by this parameter. The model can demonstrate oscillatory behavior in
its approach to the stationary state. These oscillations are also present in
the mean-field approximation which is a first-order differential equation with
time-delay. Studying dynamical critical exponents suggests that the model
belongs to the DP universlity class.Comment: 4 pages, 5 figures, to be published in Phys. Rev.
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