158 research outputs found
Clumpy Neutralino Dark Matter
We investigate the possibility to detect neutralino dark matter in a scenario
in which the galactic dark halo is clumpy. We find that under customary
assumptions on various astrophysical parameters, the antiproton and continuum
gamma-ray signals from neutralino annihilation in the halo put the strongest
limits on the clumpiness of a neutralino halo. We argue that indirect detection
through neutrinos from the Earth and the Sun should not be much affected by
clumpiness. We identify situations in parameter space where the gamma-ray line,
positron and diffuse neutrino signals from annihilations in the halo may
provide interesting signals in upcoming detectors.Comment: 19 pages, 10 eps-figures (included), LaTeX, uses RevTe
Astrophysical inputs on the SUSY dark matter annihilation detectability
If dark matter (DM), which is considered to constitute most of the mass of
galaxies, is made of supersymmetric (SUSY) particles, the centers of galaxies
should emit gamma-rays produced by their self-annihilation. We present accurate
estimates of continuum gamma-ray fluxes due to neutralino annihilation in the
central regions of the Milky Way. We use detailed models of our Galaxy, which
satisfy available observational data, and include some important physical
processes, which were previously neglected. Our models predict that spatially
extended annihilation signal should be detected at high confidence levels by
incoming experiments assuming that neutralinos make up most of the DM in the
Universe and that they annihilate according to current SUSY models.Comment: 4 pages, submitted to Physical Review Letter
Possible Indications of a Clumpy Dark Matter Halo
We investigate if the gamma ray halo, for which recent evidence has been
found in EGRET data, can be explained by neutralino annihilations in a clumpy
halo. We find that the measured excess gamma ray flux can be explained through
a moderate amount of clumping in the halo. Moreover, the required amount of
clumping implies also a measureable excess of antiprotons at low energies, for
which there is support from recent measurements by the BESS collaboration. The
predicted antiproton fluxes resulting from neutralino annihilations in a clumpy
halo are high enough to give an excess over cosmic-ray produced antiprotons
also at moderately high energies (above a few GeV). This prediction, as well as
that of one or two sharp gamma lines coming from annihilations into 2 gammas or
Z gamma can be tested in upcoming space-borne experiments like AMS and GLAST.Comment: 5 pages, 3 eps-figures (included), LaTeX, uses RevTe
The Minimal Model for Dark Matter and Unification
Gauge coupling unification and the success of TeV-scale weakly interacting
dark matter are usually taken as evidence of low energy supersymmetry (SUSY).
However, if we assume that the tuning of the higgs can be explained in some
unnatural way, from environmental considerations for example, SUSY is no longer
a necessary component of any Beyond the Standard Model theory. In this paper we
study the minimal model with a dark matter candidate and gauge coupling
unification. This consists of the SM plus fermions with the quantum numbers of
SUSY higgsinos, and a singlet. It predicts thermal dark matter with a mass that
can range from 100 GeV to around 2 TeV and generically gives rise to an
electric dipole moment that is just beyond current experimental limits, with a
large portion of its allowed parameter space accessible to next generation EDM
and direct detection experiments. We study precision unification in this model
by embedding it in a 5-D orbifold GUT where certain large threshold corrections
are calculable, achieving gauge coupling and b-tau unification, and predicting
a rate of proton decay just beyond current limits.Comment: 20 pages, 10 figures. v2: Minor typos and Reference errors corrected.
Modified explanation of the KK mode contribution to runnin
Neutralino Dark Matter beyond CMSSM Universality
We study the effect of departures from SUSY GUT universality on the
neutralino relic density and both its direct detection and indirect detection,
especially by neutrino telescopes. We find that the most interesting models are
those with a value of lower than the universal case.Comment: 20 pages, 12 figures, JHEP format. Figures improved for B&W,
references added, typos and english correcte
Dark Matter Capture in the First Stars: a Power Source and Limit on Stellar Mass
The annihilation of weakly interacting massive particles can provide an
important heat source for the first (Pop. III) stars, potentially leading to a
new phase of stellar evolution known as a "Dark Star". When dark matter (DM)
capture via scattering off of baryons is included, the luminosity from DM
annihilation may dominate over the luminosity due to fusion, depending on the
DM density and scattering cross-section. The influx of DM due to capture may
thus prolong the lifetime of the Dark Stars. Comparison of DM luminosity with
the Eddington luminosity for the star may constrain the stellar mass of zero
metallicity stars; in this case DM will uniquely determine the mass of the
first stars. Alternatively, if sufficiently massive Pop. III stars are found,
they might be used to bound dark matter properties.Comment: 19 pages, 4 figures, 3 Tables updated captions and graphs, corrected
grammer, and added citations revised for submission to JCA
A Dark Matter Candidate from an Extra (Non-Universal) Dimension
We show that a recently constructed five-dimensional (5D) model with
gauge-Higgs unification and explicit Lorentz symmetry breaking in the bulk,
provides a natural dark matter candidate. This is the lightest Kaluza-Klein
particle odd under a certain discrete Z_2 symmetry, which has been introduced
to improve the naturalness of the model, and resembles KK-parity but is less
constraining.
The dark matter candidate is the first KK mode of a 5D gauge field and
electroweak bounds force its mass above the TeV scale. Its pair annihilation
rate is too small to guarantee the correct relic abundance; however
coannihilations with colored particles greatly enhance the effective
annihilation rate, leading to realistic relic densities.Comment: 26 pages, 10 figures; v2: fig.1 corrected, one reference and some
comments added, conclusions unchanged. Version to appear in JHE
Partial wave treatment of Supersymmetric Dark Matter in the presence of CP - violation
We present an improved partial wave analysis of the dominant LSP annihilation
channel to a fermion-antifermion pair which avoids the non-relativistic
expansion being therefore applicable near thresholds and poles. The method we
develop allows of contributions of any partial wave in the total angular
momentum J in contrast to partial wave analyses in terms of the orbital angular
momentum L of the initial state, which is usually truncated to p-waves, and
yields very accurate results. The method is formulated in such a way as to
allow easy handling of CP-violating phases residing in supersymmetric
parameters. We apply this refined partial wave technique in order to calculate
the neutralino relic density in the constrained MSSM (CMSSM) in the presence of
CP-violating terms occurring in the Higgs - mixing parameter \mu and trilinear
A coupling for large tanb. The inclusion of CP-violating phases in mu and A
does not upset significantly the picture and the annihilation of the LSP's to a
b b_bar, through Higgs exchange, is still the dominant mechanism in obtaining
cosmologically acceptable neutralino relic densities in regions far from the
stau-coannihilation and the `focus point'. Significant changes can occur if we
allow for phases in the gaugino masses and in particular the gluino mass.Comment: 23 pages LaTeX, 10 eps figures, version to appear in PR
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