1,720,994 research outputs found
SUSY dark matter and quintessence
No full textWe investigate the enhancement of neutralino relic density in the context of a realistic cosmological scenario with quintessence. The accurate relic density computation we perform allows us to be sensitive to cases with both shifts in the abundance at the per cent level, and enhancements as large as 10(6). We thoroughly analyse the dependence on the supersymmetric spectrum and on the mass and composition of the lightest neutralino. We point out that supersymmetric models yielding a wino- or higgsino-like lightest neutralino become cosmologically appealing in the presence of quintessence
Multi-wavelength signals of dark matter annihilations at the Galactic center
No full textWe perform a systematic study of the multi-wavelength signal induced by weakly interacting massive particle (WIMP) annihilations at the Galactic Center (GC). Referring to a generic WIMP dark matter (DM) scenario and depending on astrophysical inputs, we discuss spectral and angular features and sketch correlations among signals in the different energy bands. None of the components which have been associated to the GC source Sgr A*, nor the diffuse emission components from the GC region, have spectral or angular features typical of a DM source. Still, data-sets at all energy bands, namely, the radio, near infrared, X-ray and gamma-ray bands, contribute to place significant constraints on the WIMP parameter space. In general, the gamma-ray energy range is not the one with the largest signal to background ratio. In the case of large magnetic fields close to the GC, X-ray data give the tightest bounds. The emission in the radio-band, which is less model dependent, is very constraining as well. The recent detection by HESS of a GC gamma-ray source, and of a diffuse gamma-ray component, limits the possibility of a DM discovery with next generation of gamma-ray telescopes, like GLAST and CTA. We find that the most of the region in the parameter space accessible to these instruments is actually already excluded at other wave-lenghts. On the other hand, there may be still an open window to improve constraints with wide-field radio observations
The role of antimatter searches in the hunt for supersymmetric dark matter
No full textWe analyse the antimatter yield of supersymmetric (SUSY) models with large neutralino annihilation cross sections. We introduce three benchmark scenarios, featuring bino, wino and higgsino-like lightest neutralinos, respectively, and we study in detail the resulting antimatter spectral features. We carry out a systematic and transparent comparison between current and future prospects for direct detection, neutrino telescopes and antimatter searches. We demonstrate that often, in the models we consider, antimatter searches are the only detection channels that already constrain the SUSY parameter space. In particular large antiprotons fluxes are expected for wino-like lightest neutralinos, while significant antideuteron fluxes result from resonantly annihilating binos. We introduce a simple and general recipe which allows us to assess the visibility of a given SUSY model at future antimatter search facilities. We provide evidence that upcoming space-based experiments, like PAMELA or AMS, are going to be, in many cases, the unique open road towards dark matter discovery
Spin-Dependent WIMPs in DAMA?
No full textWe investigate whether the annual modulation observed in the DAMA experiment can be due to a weakly-interacting massive particle (WIMP) with an axial-vector (spin-dependent; SD) coupling to nuclei. We evaluate the SD WIMP-proton cross section under the assumption that such scattering accounts for the DAMA modulation, and we do the same for a SD WIMP-neutron cross section. We show that SD WIMP-proton scattering is ruled out in a model-independent fashion by null searches for energetic neutrinos from WIMP annihilation in the Sun, and that SD WIMP-neutron scattering is ruled out for WIMP masses greater than or similar to 20 GeV by the null result with the DAMA Xe detector. A SD WIMP with mass less than or similar to 20 GeV is still compatible, but only if the SD WIMP-neutron interaction is four orders of magnitude greater than the WIMP-proton interaction
Direct versus indirect detection in mSUGRA with self-consistent halo models
No full textWe perform a detailed analysis of the detection prospects of neutralino dark matter in the mSUGRA framework. We focus on models with a thermal relic density, estimated with high accuracy using the DarkSUSY package, in the range favoured by current precision cosmological measurements. Direct and indirect detection rates are computed implementing two models for the dark matter halo, tracing opposite regimes for the phase of baryon infall, with fully consistent density profiles and velocity distribution functions. This has allowed, for the first time, a fully consistent comparison between direct and indirect detection prospects. We discuss all relevant regimes in the mSUGRA parameter space, underlining relevant effects, and providing the basis for extending the discussion to alternative frameworks. In general, we find that direct detection and searches for antideuterons in the cosmic rays seems to be the most promising ways to search for neutralinos in these scenarios
Phenomenological consequences of an interacting multicomponent dark sector
Full text linkWe consider a dark sector model containing stable fermions charged under an unbroken U(1) gauge interaction, with a massless dark photon as force carrier, and interacting with ordinary matter via scalar messengers. We study its early Universe evolution by solving a set of coupled Boltzmann equations that track the number density of the different species, as well as entropy and energy exchanges between the dark and visible sectors. Phenomenologically viable realizations include: (i) a heavy (order 1 TeV or more) leptonlike dark fermion playing the role of the dark matter candidate, with various production mechanisms active depending on the strength of the dark-visible sector portal; (ii) light (few GeV to few tens of GeV) quarklike dark fermions, stable but with suppressed relic densities; (iii) an extra radiation component in Universe due to dark photons, with temperature constrained by cosmic microwave background data, and in turn preventing dark fermions to be lighter than about 1 GeV. Extra constraints on our scenario stem from dark matter direct detection searches: the elastic scattering on nuclei is driven by dipole or charge radius interactions mediated by either Standard Model or dark photons, providing long-range effects which, however, are not always dominant, as usually assumed in this context. Projected sensitivities for next-generation detectors cover a significant portion of the viable parameter space and are competitive with respect to the model-dependent constraints derived from the magnetic dipole moments of leptons and cooling of stellar systems
Velocity distributions and annual-modulation signatures of weakly-interacting massive particles
Full text linkAn annual modulation in the event rate of the NaI detector of the DAMA collaboration has been used to infer the existence of particle dark matter in the Galactic halo. Bounds on the WIMP mass and WIMP-nucleon cross section have been derived. These analyses have assumed that the local dark-matter velocity distribution is either isotropic or has some bulk rotation. Here we consider the effects of possible structure in the WIMP velocity distribution on the annual-modulation amplitude. We show that if we allow for a locally anisotropic velocity dispersion tensor, the interpretation of direct detection experiments could be altered significantly. We also show that uncertainties in the velocity distribution function that arise from uncertainties in the radial density profile are less important if the velocity dispersion is assumed to be isotropic
Neutralino Dark Matter Detection in Split Supersymmetry
No full textWe study the phenomenology of neutralino dark matter within generic supersymmetric
scenarios where the Gaugino and Higgsino masses are much lighter than
the scalar soft breaking masses (Split Supersymmetry). We consider a low-energy
model-independent approach and show that the guidelines in the definition of this
general framework come from cosmology, which forces the lightest neutralino to
have a mass smaller than 2.2 TeV. The testability of the framework is addressed
by discussing all viable dark matter detection techniques. Current data on cosmic
rays antimatter, gamma-rays and on the abundance of primordial 6Li already
set significant constraints on the parameter space. Complementarity among future
direct detection experiments, indirect searches for antimatter and with neutrino
telescopes, and tests of the theory at future accelerators, such as the LHC and a
NLC, is highlighted. In particular, we study in detail the regimes of Wino-Higgsino
mixing and Bino-Wino transition, which have been most often neglected in the past.
We emphasize that our analysis may apply to more general supersymmetric models
where scalar exchanges do not provide the dominant contribution to annihilation
rates
Possible indications of a clumpy dark matter halo
No full textWe 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. The required amount of clumping implies also a measurable excess of antiprotons at low energies, which may be suggested by 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 gamma gamma or Z gamma, can be tested in upcoming space-home experiments such as AMS and GLAST
Cosmic antiprotons as a probe for supersymmetric dark matter ?
Full text linkThe flux of cosmic-ray antiprotons from neutralino annihilations in the Galactic halo is computed for a large sample of models in the minimal supersymmetric extension of the standard model (MSSM). 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 current data. However, allowing for a signal by playing with the uncertainties in the background estimate, we discuss the characteristic features of the supersymmetric models that 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, on the other hand, allow the exclusion of any of the MSSM models we consider on the basis of data. In addition to numerical results, we also present 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 set a limit on the antiproton lifetime from present measurements, since the injection of antiprotons from neutralino annihilation can compensate for the loss from decay
- …
