15 research outputs found
Spectral Gamma-ray Signatures of Cosmological Dark Matter Annihilation
We propose a new signature for weakly interacting massive particle (WIMP)
dark matter, a spectral feature in the diffuse extragalactic gamma-ray
radiation. This feature, a sudden drop of the gamma-ray intensity at an energy
corresponding to the WIMP mass, comes from the asymmetric distortion of the
line due to WIMP annihilation into two gamma-rays caused by the cosmological
redshift. Unlike other proposed searches for a line signal, this method is not
very sensitive to the exact dark matter density distribution in halos and
subhalos. The only requirement is that the mass distribution of substructure on
small scales follows approximately the Press-Schechter law, and that smaller
halos are on the average denser than large halos, which is a generic outcome of
N-body simulations of Cold Dark Matter, and which has observational support.
The upcoming Gamma-ray Large Area Space Telescope (GLAST) will be eminently
suited to search for these spectral features. For numerical examples, we use
rates computed for supersymmetric particle dark matter, where a detectable
signal is possible.Comment: 4 pages, 1 figure. Matches the published version. Conclusions
unchange
DarkSUSY - A numerical package for dark matter calculations in the MSSM
The question of the nature of the dark matter in the Universe remains one of
the most outstanding unsolved problems in basic science. One of the best
motivated particle physics candidates is the lightest supersymmetric particle,
assumed to be the lightest neutralino. We here describe DarkSUSY, an advanced
numerical FORTRAN package for supersymmetric dark matter calculations which we
release for public use. With the help of this package, the masses and
compositions of various supersymmetric particles can be computed, for given
input parameters of the minimal supersymmetric extension of the Standard Model
(MSSM). For the lightest neutralino, the relic density is computed, using
accurate methods which include the effects of resonances, pair production
thresholds and coannihilations. Accelerator bounds are checked to identify
viable dark matter candidates. Finally, detection rates are computed for a
variety of detection methods, such as direct detection and indirect detection
through antiprotons, gamma-rays and positrons from the Galactic halo or
neutrinos from the center of the Earth or the Sun.Comment: 6 pages, no figures. Contribution to the proceedings of the 3rd
International Workshop on the Identification of Dark Matter (IDM2000) in
York, in pres
Implications of a New Solar System Population of Neutralinos on Indirect Detection Rates
Recently, a new Solar System population of weakly interacting massive
particle (WIMP) dark matter has been proposed to exist. We investigate the
implications of this population on indirect signals in neutrino telescopes (due
to WIMP annihilations in the Earth) for the case when the WIMP is the lightest
neutralino of the MSSM, the minimal supersymmetric extension of the standard
model. The velocity distribution and capture rate of this new population is
evaluated and the flux of neutrino-induced muons from the center of the Earth
in neutrino telescopes is calculated. The strength of the signal is very
sensitive to the velocity distribution of the new population. We analytically
estimate this distribution using the approximate conservation of the component
of the WIMP angular momentum orthogonal to the ecliptic plane. The non-linear
problem of combining a fixed capture rate from the standard galactic WIMP
population with one rising linearly with time from the new population to obtain
the present-day annihilation rate in the Earth is also solved analytically. We
show that the effects of the new population can be crucial for masses below
around 150 GeV, where enhancements of the predicted muon flux from the center
of the Earth by up to a factor of 100 compared to previously published
estimates occur. As a result of the new WIMP population, the next generation of
neutrino telescopes should be able to probe a much larger region of parameter
space in the mass range 60-130 GeV.Comment: 21 pages, 5 eps figures, uses JHEP.cls. Figures made more readable,
references updated. Matches published versio
A new population of WIMPs in the solar system and indirect detection rates
A new Solar System population of Weakly Interacting Massive Particle (WIMP)
dark matter has been proposed to exist. We investigate the implications of this
population on indirect signals in neutrino telescopes (due to WIMP
annihilations in the Earth) for the case when the WIMP is the lightest
neutralino of the MSSM, the minimal supersymmetric extension of the standard
model. The velocity distribution and capture rate of this new population is
evaluated and the flux of neutrino-induced muons from the center of the Earth
in neutrino telescopes is calculated. We show that the effects of the new
population can be crucial for masses around 60-120 GeV, where enhancements of
the predicted muon flux from the center of the Earth by up to a factor of 100
compared to previously published estimates occur. As a result of the new WIMP
population, neutrino telescopes should be able to probe a much larger region of
parameter space in this mass range.Comment: 6 pages, 4 figures. Contribution to the proceedings of the 3rd
International Workshop on the Identification of Dark Matter (IDM2000) in
York, in pres
Early search for supersymmetric dark matter models at the LHC without missing energy
We investigate early discovery signals for supersymmetry at the Large Hadron
Collider without using information about missing transverse energy. Instead we
use cuts on the number of jets and isolated leptons (electrons and/or muons).
We work with minimal supersymmetric extensions of the standard model, and focus
on phenomenological models that give a relic density of dark matter compatible
with the WMAP measurements. An important model property for early discovery is
the presence of light sleptons, and we find that for an integrated luminosity
of only 200--300 pb at a center-of-mass energy of 10 TeV models with
gluino masses up to GeV can be tested.Comment: 28 pages, 12 figures; published versio
COMP (Cartilage Oligomeric Matrix Protein) Neoepitope A Novel Biomarker to Identify Symptomatic Carotid Stenosis
Objective:COMP (cartilage oligomeric matrix protein) is abundantly expressed in the cardiovascular system, cartilage, and atherosclerotic plaques. We investigated if the total COMP (COMPtotal) and COMP neoepitope (COMPneo) with other cardiovascular markers and clinical parameters could identify symptomatic carotid stenosis.Approach and Results:Blood samples were collected from patients with symptomatic carotid stenosis (stenosis, n=50), patients with stroke without carotid stenosis but small plaques (plaque, n=50), and control subjects (n=50). COMPtotal and COMPneo were measured using an ELISA. Ninety-two cardiovascular disease markers were measured by the Olink CVD kit. The presence of native COMP and COMPneo was determined by immunohistochemistry. The concentration of COMPneo was higher and COMPtotal was lower in the stenosis group. When the concentration was compared between the stenosis and control groups, IL-1ra (interleukin-1 receptor antagonist protein), IL6 (interleukin-6), REN (Renin), MMP1 (matrix metalloproteinase-1), TRAIL-R2 (tumor necrosis factor-related apoptosis-inducing ligand receptor 2), ITGB1BP2 (integrin beta 1 binding protein 2), and COMPneo were predictive of stenosis. Conversely, KLK6 (kallikrein-6), COMPtotal, NEMO (nuclear factor-kappa-B essential modulator), SRC (Proto-oncogene tyrosine-protein kinase Src), SIRT2 (SIR2-like protein), CD40 (cluster of differentiation 40), TF (tissue factor), MP (myoglobin), and RAGE (receptor for advanced glycation end-products) were predictive of the control group. Model reproducibility was good with the receiver operating characteristic plot area under the curve being 0.86. When comparing the plaque group and stenosis group, COMPneo, GAL (galanin), and PTX3 (pentraxin-related protein PTX3) were predictive of stenosis. Model reproducibility was excellent (receiver operating characteristic plot area under the curve 0.92). COMPneo was detected in smooth muscle-, endothelial-, and foam-cells in carotid stenosis.Conclusions:Degradation of COMP may be associated with atherosclerosis progression and generation of a specific COMP fragment-COMPneo. This may represent a novel biomarker that together with COMPtotal and other risk-markers could be used to identify symptomatic carotid stenosis
Cosmic antiprotons as a probe for supersymmetric dark matter?
The flux of cosmic ray antiprotons from neutralino annihilations in the
galactic halo is computed for a large sample of models in the MSSM (the Minimal
Supersymmetric extension of the Standard Model). We also revisit the problem of
estimating the background of low-energy cosmic ray induced secondary
antiprotons, taking into account their subsequent interactions (and energy
loss) and the presence of nuclei in the interstellar matter.
We consider a two-zone diffusion model, with and without a galactic wind. We
find that, given the uncertainties in the background predictions, there is no
need for a primary (exotic) component to explain present data. However,
allowing for a signal by playing with the uncertainties in the background
estimate, we discuss the characteristic features of the supersymmetric models
which give a satisfactory description of the data. We point out that in some
cases the optimal kinetic energy to search for a signal from supersymmetric
dark matter is above several GeV, rather than the traditional sub-GeV region.
The large astrophysical uncertainties involved do not, one the other hand,
allow the exclusion of any of the MSSM models we consider, on the basis of
data.
We present besides numerical results also convenient parameterizations of the
antiproton yields of all `basic' two-body final states. We also give examples
of the yield and differential energy spectrum for a set of supersymmetric
models with high rates.
We also remark that it is difficult to put a limit on the antiproton lifetime
from present measurements, since the injection of antiprotons from neutralino
annihilation can compensate the loss from decay.Comment: 22 pages, 11 figures, uses emulateapj.st
Statistical coverage for supersymmetric parameter estimation: a case study with direct detection of dark matter
Models of weak-scale supersymmetry offer viable dark matter (DM) candidates.
Their parameter spaces are however rather large and complex, such that pinning
down the actual parameter values from experimental data can depend strongly on
the employed statistical framework and scanning algorithm. In frequentist
parameter estimation, a central requirement for properly constructed confidence
intervals is that they cover true parameter values, preferably at exactly the
stated confidence level when experiments are repeated infinitely many times.
Since most widely-used scanning techniques are optimised for Bayesian
statistics, one needs to assess their abilities in providing correct confidence
intervals in terms of the statistical coverage. Here we investigate this for
the Constrained Minimal Supersymmetric Standard Model (CMSSM) when only
constrained by data from direct searches for dark matter. We construct
confidence intervals from one-dimensional profile likelihoods and study the
coverage by generating several pseudo-experiments for a few benchmark sets of
pseudo-true parameters. We use nested sampling to scan the parameter space and
evaluate the coverage for the benchmarks when either flat or logarithmic priors
are imposed on gaugino and scalar mass parameters. The sampling algorithm has
been used in the configuration usually adopted for exploration of the Bayesian
posterior. We observe both under- and over-coverage, which in some cases vary
quite dramatically when benchmarks or priors are modified. We show how most of
the variation can be explained as the impact of explicit priors as well as
sampling effects, where the latter are indirectly imposed by physicality
conditions. For comparison, we also evaluate the coverage for Bayesian credible
intervals, and observe significant under-coverage in those cases.Comment: 30 pages, 5 figures; v2 includes major updates in response to
referee's comments; extra scans and tables added, discussion expanded, typos
corrected; matches published versio