| 1. |
- Balazs, Csaba, et al.
(författare)
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Interpreting the Fermi-LAT gamma ray excess in the simplified framework
- 2015
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Ingår i: Physical Review D. - : American Physical Society. - 1550-7998 .- 1550-2368. ; 92:12
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Tidskriftsartikel (refereegranskat)abstract
- We test the plausibility of the hypothesis that the annihilation of a Majorana fermion dark matter particle via a scalar mediator explains the gamma ray excess from the Galactic center. Assuming that the mediator couples to all third generation fermions we calculate observables for dark matter abundance and scattering on nuclei, gamma, positron, and antiproton cosmic ray fluxes, radio emission from dark matter annihilation, and the effect of dark matter annihilations on the CMB. After discarding the controversial radio observation, we show that the dark matter model simultaneously fits the observed excesses in the cosmic gamma ray, the positron, and antiproton fluxes, while evading constraints from the CMB and direct detection. The experimental data are consistent with a dark matter (mediator) mass in the 10-100 (3-1000) GeV region and with weakly correlated couplings to bottom quarks and tau leptons with values of 10(-3) - 1 at the 68% credibility level.
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| 2. |
- De Moya, Robert S., et al.
(författare)
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Interrelationships and diversification of Argynnis Fabricius and Speyeria Scudder butterflies
- 2017
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Ingår i: Systematic Entomology. - : Wiley. - 0307-6970. ; 42:4, s. 635-649
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Tidskriftsartikel (refereegranskat)abstract
- Diverse radiations of insects are often associated with adaptations to host plants, and well-resolved phylogenetic relationships are required to fully understand them. Palearctic Argynnis and related subgenera, together with North American Speyeria butterflies make up a radiation whose species hypotheses are confounded by shared wing colour patterns between sympatric populations of closely related recognized species. Previous studies of this group indicate that Speyeria is a lineage within Argynnis, but sampling in these studies has either involved too few Speyeria species or incomplete sampling of Argynnis species. Thus, no comprehensive phylogenetic analysis exists for all members that answers the question of monophyly of Speyeria, or other subgeneric taxa, and their relationship to Argynnis species. We completed a phylogenetic analysis of all North American Speyeria species and all but one species within Argynnis, using one mitochondrial (cytochrome c oxidase I, COI) and four nuclear genes [elongation factor 1 alpha (EF1α), wingless (WG), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and ribosomal protein S5 (RPS5)]. The results indicate three major lineages within Argynnis s.l.: two Palearctic and one containing both Palearctic and Nearctic species. In summary, the phylogenetic analyses suggest the need for reorganization into three natural groups: Argynnis, Fabriciana and Speyeria. Within each of these genera the phylogenetic hypothesis indicates an evolutionary history marked by rapid diversification and potential extinction, followed by ongoing lineage sorting. The position of North American Speyeria is nested within the Palearctic lineages, which indicates that the radiation began in Asia and was fuelled by existing Viola diversity in North America. Dating analyses of Viola and Speyeria corroborate this hypothesis. The current North American Speyeria species are mixed on the tree, indicating a recent and ongoing radiation. These results provide needed clarity on the evolution of this group, which contains species of conservation concern.
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| 3. |
- Kelso, Chris, et al.
(författare)
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The impact of baryons on the direct detection of dark matter
- 2016
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP PUBLISHING LTD. - 1475-7516. ; :8
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Tidskriftsartikel (refereegranskat)abstract
- The spatial and velocity distributions of dark matter particles in the Milky Way Halo affect the signals expected to be observed in searches for dark matter. Results from direct detection experiments are often analyzed assuming a simple isothermal distribution of dark matter, the Standard Halo Model (SHM). Yet there has been skepticism regarding the validity of this simple model due to the complicated gravitational collapse and merger history of actual galaxies. In this paper we compare the SHM to the results of cosmological hydrodynamical simulations of galaxy formation to investigate whether or not the SHM is a good representation of the true WIMP distribution in the analysis of direct detection data. We examine two Milky Way-like galaxies from the MaGICC cosmological simulations (a) with dark matter only and (b) with baryonic physics included. The inclusion of baryons drives the shape of the DM halo to become more spherical and makes the velocity distribution of dark matter particles less anisotropic especially at large heliocentric velocities, thereby making the SHM a better fit. We also note that we do not find a significant disk-like rotating dark matter component in either of the two galaxy halos with baryons that we examine, suggesting that dark disks are not a generic prediction of cosmological hydrodynamical simulations. We conclude that in the Solar neighborhood, the SHM is in fact a good approximation to the true dark matter distribution in these cosmological simulations (with baryons) which are reasonable representations of the Milky Way, and hence can also be used for the purpose of dark matter direct detection calculations.
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| 4. |
- Silverwood, Hamish, et al.
(författare)
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Sensitivity of IceCube-DeepCore to Neutralino Dark Matter in the MSSM-25
- 2013
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; 03, s. 023-
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Tidskriftsartikel (refereegranskat)abstract
- We analyse the sensitivity of IceCube-DeepCore to annihilation of neutralino dark matter in the solar core, generated within a 25 parameter version of the minimally supersymmetric standard model (MSSM-25). We explore the 25-dimensional parameter space using scanning methods based on importance sampling and using DarkSUSY 5.0.6 to calculate observables. Our scans produced a database of 6.02 million parameter space points with neutralino dark matter consistent with the relic density implied by WMAP 7-year data, as well as with accelerator searches. We performed a model exclusion analysis upon these points using the expected capabilities of the IceCube-DeepCore Neutrino Telescope. We show that IceCube-DeepCore will be sensitive to a number of models that are not accessible to direct detection experiments such as SIMPLE, COUPP and XENON100, indirect detection using Fermi-LAT observations of dwarf spheroidal galaxies, nor to current LHC searches.
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