We investigate the sensitivity of the Gamma-ray Large Area Space Telescope(GLAST) to indirectly detect weakly interacting massive particles (WIMPs)through the $\gamma$-ray signal that their pair ...annihilation produces. WIMPsare among the favorite candidates to explain the compelling evidence that about80% of the mass in the Universe is non-baryonic dark matter (DM). They areserendipitously motivated by various extensions of the standard model ofparticle physics such as Supersymmetry and Universal Extra Dimensions (UED).With its unprecedented sensitivity and its very large energy range (20 MeV tomore than 300 GeV) the main instrument on board the GLAST satellite, the LargeArea Telescope (LAT), will open a new window of discovery. As our estimatesshow, the LAT will be able to detect an indirect DM signature for a large classof WIMP models given a cuspy profile for the DM distribution. Using the currentstate of the art Monte Carlo and event reconstruction software developed withinthe LAT collaboration, we present preliminary sensitivity studies for severalpossible sources inside and outside the Galaxy. We also discuss the potentialof the LAT to detect UED via the electron/positron channel. Diffuse backgroundmodeling and other background issues that will be important in setting limitsor seeing a signal are presented.
A
bstract
It is well known that the annihilation of Majorana dark matter into fermions is helicity suppressed. Here, we point out that the underlying mechanism is a subtle combination of two distinct ...effects, and we present a comprehensive analysis of how the suppression can be partially or fully lifted by the internal bremsstrahlung of an additional boson in the final state. As a concrete illustration, we compute analytically the full amplitudes and annihilation rates of supersymmetric neutralinos to final states that contain any combination of two standard model fermions, plus one electroweak gauge boson or one of the five physical Higgs bosons that appear in the minimal supersymmetric standard model. We classify the various ways in which these three-body rates can be large compared to the two-body rates, identifying cases that have not been pointed out before. In our analysis, we put special emphasis on how to avoid the double counting of identical kinematic situations that appear for two-body and three-body final states, in particular on how to correctly treat differential rates and the spectrum of the resulting stable particles that is relevant for indirect dark matter searches. We find that both the total annihilation rates and the yields can be significantly enhanced when taking into account the corrections computed here, in particular for models with somewhat small annihilation rates at tree-level which otherwise would not be testable with indirect dark matter searches. Even more importantly, however, we find that the resulting annihilation spectra of positrons, neutrinos, gamma-rays and antiprotons differ in general substantially from the model-independent spectra that are commonly adopted, for these final states, when constraining particle dark matter with indirect detection experiments.
Gamma rays from kaluza-klein dark matter BERGSTRÖM, Lars; BRINGMANN, Torsten; ERIKSSON, Martin ...
Physical review letters,
04/2005, Volume:
94, Issue:
13
Journal Article
Peer reviewed
Open access
A TeV gamma-ray signal from the direction of the Galactic center (GC) has been detected by the HESS experiment. Here, we investigate whether Kaluza-Klein (KK) dark matter annihilations near the GC ...can be the explanation. Including the contributions from internal bremsstrahlung as well as subsequent decays of quarks and tau leptons, we find a very flat gamma-ray spectrum which drops abruptly at the dark matter particle mass. For a KK mass of about 1 TeV, this gives a good fit to the HESS data below 1 TeV. A similar model, with gauge coupling roughly 3 times as large and a particle mass of about 10 TeV, would give both the correct relic density and a photon spectrum that fits the complete range of data.
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We consider the gamma-ray spectrum from neutralino dark matter annihilations and show that internal bremsstrahlung of pair final states gives a previously neglected source of photons at energies near ...the mass of the neutralino. For masses larger than about 1 TeV, and for present day detector resolutions, this results in a characteristic signal that may dominate not only over the continuous spectrum from W fragmentation, but also over the gammagamma and gammaZ line signals which are known to give large rates for heavy neutralinos. Observational prospects thus seem promising.
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