301 research outputs found
Which fraction of the measured cosmic-ray antiprotons might be due to neutralino annihilation in the galactic halo?
We analyze the data of low-energy cosmic-ray antiproton spectrum, recently
published by the BESS Collaboration, in terms of newly calculated fluxes for
secondary antiprotons and for a possible contribution of an exotic signal due
to neutralino annihilation in the galactic halo. We single out the relevant
supersymmetric configurations and discuss their explorability with experiments
of direct search for particle dark matter and at accelerators. We discuss how
future measurements with the Alpha Magnetic Spectrometer (AMS) on the Shuttle
flight may disentangle the possible neutralino-induced contribution from the
secondary one.Comment: 25 pages, ReVTeX, 18 figures (high resolution figures available upon
request
Positrons from dark matter annihilation in the galactic halo: uncertainties
Indirect detection signals from dark matter annihilation are studied in the
positron channel. We discuss in detail the positron propagation inside the
galactic medium: we present novel solutions of the diffusion and propagation
equations and we focus on the determination of the astrophysical uncertainties
which affect the positron dark matter signal. We show that, especially in the
low energy tail of the positron spectra at Earth, the uncertainty is sizeable
and we quantify the effect. Comparison of our predictions with current
available and foreseen experimental data are derived.Comment: 4 pages, 4 figures, Proc. of the 30th International Cosmic Ray
Conference, July 3 - 11, 2007, Merida, Yucatan, Mexico (ICRC07
Positrons from dark matter annihilation in the galactic halo: theoretical uncertainties
Indirect detection signals from dark matter annihilation are studied in the
positron channel. We discuss in detail the positron propagation inside the
galactic medium: we present novel solutions of the diffusion and propagation
equations and we focus on the determination of the astrophysical uncertainties
which affect the positron dark matter signal. We find dark matter scenarios and
propagation models that nicely fit existing data on the positron fraction.
Finally, we present predictions both on the positron fraction and on the flux
for already running or planned space experiments, concluding that they have the
potential to discriminate a possible signal from the background and, in some
cases, to distinguish among different astrophysical propagation models.Comment: 22 pages, 15 figures. A few comments and references adde
Observations of annual modulation in direct detection of relic particles and light neutralinos
The long-standing model-independent annual modulation effect measured by the
DAMA Collaboration, which fulfills all the requirements of a dark matter annual
modulation signature, and the new result by the CoGeNT experiment that shows a
similar behavior are comparatively examined under the hypothesis of a dark
matter candidate particle interacting with the detectors' nuclei by a coherent
elastic process. The ensuing physical regions in the plane of the dark
matter-particle mass versus the dark matter-particle nucleon cross-section are
derived for various galactic halo models and by taking into account the impact
of various experimental uncertainties. It is shown that the DAMA and the CoGeNT
regions agree well between each other and are well fitted by a supersymmetric
model with light neutralinos which satisfies all available experimental
constraints, including the most recent results from CMS and ATLAS at the CERN
Large Hadron Collider.Comment: 13 pages, 7 figure
Long-Range Forces in Direct Dark Matter Searches
We discuss the positive indications of a possible dark matter signal in
direct detection experiments in terms of a mechanism of interaction between the
dark matter particle and the nuclei occurring via the exchange of a light
mediator, resulting in a long-range interaction. We analyze the annual
modulation results observed by the DAMA and CoGeNT experiments and the observed
excess of events of CRESST. In our analysis, we discuss the relevance of
uncertainties related to the velocity distribution of galactic dark matter and
to the channeling effect in NaI. We find that a long-range force is a viable
mechanism, which can provide full agreement between the reconstructed dark
matter properties from the various experimental data sets, especially for
masses of the light mediator in the 10-30 MeV range and a light dark matter
with a mass around 10 GeV. The relevant bounds on the light mediator mass and
scattering cross section are then derived, should the annual modulation effects
be due to this class of long-range forces.Comment: 22 pages, 14 figures. v2: Matches version published on Phys.Rev.D;
analysis of CRESST to match the recent release of the new data updated,
discussion on astrophysical constraints on self-interacting dark matter
added, some typos corrected and some references added, conclusions unchanged.
v3: Few typos correcte
Dark Matter Relic Abundance and Scalar-Tensor Dark Energy
Scalar-tensor theories of gravity provide a consistent framework to
accommodate an ultra-light quintessence scalar field. While the equivalence
principle is respected by construction, deviations from General Relativity and
standard cosmology may show up at nucleosynthesis, CMB, and solar system tests
of gravity. After imposing all the bounds coming from these observations, we
consider the expansion rate of the universe at WIMP decoupling, showing that it
can lead to an enhancement of the dark matter relic density up to few orders of
magnitude with respect to the standard case. This effect can have an impact on
supersymmetric candidates for dark matter.Comment: 12 pages, 13 figures; V2: references added, matches published versio
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