| 1. |
- Bergström, Lars, et al.
(författare)
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Investigating gamma ray lines from dark matter with future observatories
- 2012
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :11, s. 025-
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Tidskriftsartikel (refereegranskat)abstract
- We study the prospects for studying line features in gamma-ray spectra with upcoming gamma-ray experiments, such as HESS-II, the Cherenkov Telescope Array (CTA), and the GAMMA-400 satellite. As an example we use the narrow feature at 130 GeV seen in public data from the Fermi-LAT satellite. We found that all three experiments should be able to confidently confirm or rule out the presence of this 130 GeV feature. If it is real, it should be confirmed with a confidence level higher than 5 sigma. Assuming it to be a spectral signature of dark matter origin, GAMMA-400, thanks to a projected energy resolution of about 1.5 % at 100 GeV, should also be able to resolve both the gamma gamma line and a corresponding Z gamma or H gamma feature, if the corresponding branching ratio is comparable to that into two photons. It will also allow to distinguish between a gamma-ray line and the similar feature resulting from internal bremsstrahlung photons.
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| 2. |
- Sivertsson, Sofia, 1982-
(författare)
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Studies of dark matter in and around stars
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There is by now compelling evidence that most of the matter in the Universe is in the form of dark matter, a form of matter quite different from the matter we experience in every day life. The gravitational effects of this dark matter have been observed in many different ways but its true nature is still unknown. In most models, dark matter particles can annihilate with each other into standard model particles; the direct or indirect observation of such annihilation products could give important clues for the dark matter puzzle. For signals from dark matter annihilations to be detectable, typically high dark matter densities are required. Massive objects, such as stars, can increase the local dark matter density both via scattering off nucleons and by pulling in dark matter gravitationally as a star forms. Annihilations within this kind of dark matter population gravitationally bound to a star, like the Sun, give rise to a gamma ray flux. For a star which has a planetary system, dark matter can become gravitationally bound also through gravitational interactions with the planets. The interplay between the different dark matter populations in the solar system is analyzed, shedding new light on dark matter annihilations inside celestial bodies and improving the predicted experimental reach. Dark matter annihilations inside a star would also deposit energy in the star which, if abundant enough, could alter the stellar evolution. This is investigated for the very first stars in the Universe. Finally, there is a possibility for abundant small scale dark matter overdensities to have formed in the early Universe. Prospects of detecting gamma rays from such minihalos, which have survived until the present day, are discussed.
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| 3. |
- Weniger, Christoph, et al.
(författare)
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CMB bounds on dark matter annihilation : Nucleon energy losses after recombination
- 2013
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 87:12, s. 123008-
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Tidskriftsartikel (refereegranskat)abstract
- We consider the propagation and energy losses of protons and antiprotons produced by dark matter annihilation at redshifts 100 < z less than or similar to 2000. In the case of dark matter annihilations into quarks, gluons and weak gauge bosons, protons and antiprotons carry about 20% of the energy injected into e(+/-) and gamma's, but their interactions are normally neglected when deriving cosmic microwave background bounds from altered recombination histories. Here, we follow numerically the energy-loss history of typical protons/antiprotons in the cosmological medium. We show that about half of their energy is channeled into photons and e(+/-), and we present a simple prescription to estimate the corresponding strengthening of the cosmic microwave background bounds on the dark matter annihilation cross section.
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