164 research outputs found
Gamma rays from dark matter
A leading hypothesis for the nature of the elusive dark matter are thermally
produced, weakly interacting massive particles that arise in many theories
beyond the standard model of particle physics. Their self-annihilation in
astrophysical regions of high density provides a potential means of indirectly
detecting dark matter through the annihilation products, which nicely
complements direct and collider searches. Here, I review the case of gamma rays
which are particularly promising in this respect: distinct and unambiguous
spectral signatures would not only allow a clear discrimination from
astrophysical backgrounds but also to extract important properties of the dark
matter particles; powerful observational facilities like the Fermi Gamma-ray
Space Telescope or upcoming large, ground-based Cherenkov telescope arrays will
be able to probe a considerable part of the underlying, e.g. supersymmetric,
parameter space. I conclude with a more detailed comparison of indirect and
direct dark matter searches, showing that these two approaches are, indeed,
complementary.Comment: 13 pages, 4 figures, World Science proceedings style. Based on an
invited talk given at the ICATPP conference on cosmic rays for particle and
astroparticle physics, Como, Italy, 7-8 Oct 201
Significant Enhancement of Neutralino Dark Matter Annihilation from Electroweak Bremsstrahlung
Indirect searches for the cosmological dark matter have become ever more
competitive during the past years. Here, we report the first full calculation
of leading electroweak corrections to the annihilation rate of supersymmetric
neutralino dark matter. We find that these corrections can be huge, partially
due to contributions that have been overlooked so far. Our results imply a
significantly enhanced discovery potential of this well motivated dark matter
candidate with current and upcoming cosmic ray experiments, in particular for
gamma rays and models with somewhat small annihilation rates at tree level.Comment: 7 pages revtex4; 4 figures. Minor changes to match published versio
Gamma Ray Signals from Dark Matter: Concepts, Status and Prospects
Weakly interacting massive particles (WIMPs) remain a prime candidate for the
cosmological dark matter (DM), even in the absence of current collider signals
that would unambiguously point to new physics below the TeV scale. The
self-annihilation of these particles in astronomical targets may leave
observable imprints in cosmic rays of various kinds. In this review, we focus
on gamma rays which we argue to play a pronounced role among the various
possible messengers. We discuss the most promising spectral and spatial
signatures to look for, give an update on the current state of gamma-ray
searches for DM and an outlook concerning future prospects. We also assess in
some detail the implications of a potential signal identification for particle
DM models as well as for our understanding of structure formation. Special
emphasis is put on the possible evidence for a 130 GeV line-like signal that
was recently identified in the data of the Fermi gamma-ray space telescope.Comment: 42 pages, 6 figures, 2 tables; updated reference list and extended
discussio
Novel direct detection constraints on light dark matter
All attempts to directly detect particle dark matter (DM) scattering on
nuclei suffer from the partial or total loss of sensitivity for DM masses in
the GeV range or below. We derive novel constraints from the inevitable
existence of a subdominant, but highly energetic, component of DM generated
through collisions with cosmic rays. Subsequent scattering inside conventional
DM detectors, as well as neutrino detectors sensitive to nuclear recoils,
limits the DM-nucleon scattering cross section to be below cm
for both spin-independent and spin-dependent scattering of light DM.Comment: 7 pages revtex4, 3 figures. Version to appear in Phys. Rev. Let
AstroFit: An Interface Program for Exploring Complementarity in Dark Matter Research
AstroFit is an interface adding astrophysical components to programs for
fitting physics beyond the Standard Model (BSM) to experimental data from
collider searches. The project aims at combining a wide range of experimental
results from indirect, direct and collider serarches for Dark Matter (DM) and
confronting it with theoretical expectations in various DM models. Here, we
introduce AstroFit and discuss first results.Comment: 6 pages, 3 figures, proceedings for the 13th ICATPP Conference on
Astroparticle, Particle, Space Physics and Detectors for Physics
Applications, Villa Olm
Improved constraints on the primordial power spectrum at small scales from ultracompact minihalos
For a Gaussian spectrum of primordial density fluctuations, ultracompact
minihalos (UCMHs) of dark matter are expected to be produced in much greater
abundance than, e.g., primordial black holes. Forming shortly after
matter-radiation equality, these objects would develop very dense and spiky
dark matter profiles. In the standard scenario where dark matter consists of
thermally-produced, weakly-interacting massive particles, UCMHs could thus
appear as highly luminous gamma-ray sources, or leave an imprint in the cosmic
microwave background by changing the reionisation history of the Universe. We
derive corresponding limits on the cosmic abundance of UCMHs at different
epochs, and translate them into constraints on the primordial power spectrum.
We find the resulting constraints to be quite severe, especially at length
scales much smaller than what can be directly probed by the cosmic microwave
background or large-scale structure observations. We use our results to provide
an updated compilation of the best available constraints on the power of
density fluctuations on all scales, ranging from the present-day horizon to
scales more than 20 orders of magnitude smaller.Comment: 7 figures, 14 pages + appendices. v2 matches version accepted for
publication in PRD; updated to WMAP normalisation, updated reionisation
limits, various other small changes. v3 slightly corrects the normalisation
used for displaying past data in Fig 6, as well as a sign typo picked up in
proof in Eq 26. All results and conclusions completely unchange
Updated cosmic-ray and radio constraints on light dark matter: Implications for the GeV gamma-ray excess at the Galactic center
The apparent gamma-ray excess in the Galactic center region and inner Galaxy
has attracted considerable interest, notably because both its spectrum and
radial distribution are consistent with an interpretation in terms of
annihilating dark matter particles with a mass of about 10-40 GeV. We confront
such an interpretation with an updated compilation of various indirect dark
matter detection bounds, which we adapt to the specific form required by the
observed signal. We find that cosmic-ray positron data strongly rule out dark
matter annihilating to light leptons, or 'democratically' to all leptons, as an
explanation of the signal. Cosmic-ray antiprotons, for which we present
independent and significantly improved limits with respect to previous
estimates, are already in considerable tension with DM annihilation to any
combination of quark final states; the first set of AMS-02 data will thus be
able to rule out or confirm the DM hypothesis with high confidence. For
reasonable assumptions about the magnetic field in the Galactic center region,
radio observations independently put very severe constraints on a DM
interpretation of the excess, in particular for all leptonic annihilation
channels.Comment: 23 pages revtex, 19 figures, 1 table. Extended discussion of
antiproton limits and added references. Matches published versio
- β¦