| 1. |
- Freese, Katherine, et al.
(författare)
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Colloquium : Annual modulation of dark matter
- 2013
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Ingår i: Reviews of Modern Physics. - : American Physical Society. - 0034-6861 .- 1539-0756. ; 85:4, s. 1561-1581
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Tidskriftsartikel (refereegranskat)abstract
- Direct detection experiments, which are designed to detect the scattering of dark matter off nuclei in detectors, are a critical component in the search for the Universe's missing matter. This Colloquium begins with a review of the physics of direct detection of dark matter, discussing the roles of both the particle physics and astrophysics in the expected signals. The count rate in these experiments should experience an annual modulation due to the relative motion of the Earth around the Sun. This modulation, not present for most known background sources, is critical for solidifying the origin of a potential signal as dark matter. The focus is on the physics of annual modulation, discussing the practical formulas needed to interpret a modulating signal. The dependence of the modulation spectrum on the particle and astrophysics models for the dark matter is illustrated. For standard assumptions, the count rate has a cosine dependence with time, with a maximum in June and a minimum in December. Well-motivated generalizations of these models, however, can affect both the phase and amplitude of the modulation. Shown is how a measurement of an annually modulating signal could teach us about the presence of substructure in the galactic halo or about the interactions between dark and baryonic matter. Although primarily a theoretical review, the current experimental situation for annual modulation and future experimental directions is briefly discussed.
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| 2. |
- Freese, Katherine, et al.
(författare)
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Dark matter collisions with the human body
- 2012
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Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 717:1-3, s. 25-28
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the interactions of Weakly Interacting Massive Particles (WIMPs) with nuclei in the human body. We are motivated by the fact that WIMPS are excellent candidates for the dark matter in the Universe. Our estimates use a 70 kg human and a variety of WIMP masses and cross-sections. The contributions from individual elements in the body are presented and it is found that the dominant contribution is from scattering off of oxygen (hydrogen) nuclei for the spin-independent (spin-dependent) interactions. For the case of 60 GeV WIMPs, we find that, of the billions of WIMPs passing through a human body per second, roughly similar to 10 WIMPs hit one of the nuclei in the human body in an average year, if the scattering is at the maximum consistent with current bounds on WIMP interactions. We also study the 10-20 GeV WIMPs with much larger cross-sections that best fit the DAMA, COGENT, and CRESST data sets and find much higher rates: in this case as many as 10(5) WIMPs hit a nucleus in the human body in an average year, corresponding to almost one a minute. Though WIMP interactions are a source of radiation in the body, the annual exposure is negligible compared to that from other natural sources (including radon and cosmic rays), and the WIMP collisions are harmless to humans.
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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. |
- Natarajan, Aravind, et al.
(författare)
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Probing dark matter streams with CoGeNT
- 2011
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:10
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Tidskriftsartikel (refereegranskat)abstract
- We examine the future sensitivity of CoGeNT to the presence of dark matter streams and find that consideration of streams in the data may lead to differences in the interpretation of the results. We show the allowed particle mass and cross section for different halo parameters, assuming spin-independent elastic scattering. As an example, we choose a stream with the same velocity profile as that of the Sagittarius stream (and in the Solar neighborhood) and find that, with an exposure of similar to 10 kg yr, the CoGeNT results can be expected to exclude the standard-halo-model-only halo in favor of a standard halo model + stream halo at the 95% (99.7%) confidence level, provided the stream contributes 3% (5%) of the local dark matter density. The presence of a significant stream component may result in incorrect estimates of the particle mass and cross section unless the presence of the stream is taken into account. We conclude that the CoGeNT experiment is sensitive to streams and care should be taken to include the possibility of streams when analyzing experimental results.
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| 5. |
- Savage, Christopher, et al.
(författare)
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XENON10/100 dark matter constraints in comparison with CoGeNT and DAMA : Examining the L(eff) dependence
- 2011
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 83:5, s. 055002-
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Tidskriftsartikel (refereegranskat)abstract
- We consider the compatibility of DAMA/LIBRA, CoGeNT, XENON10 and XENON100 results for spin-independent (SI) dark matter weakly interacting massive particles, particularly at low masses (similar to 10 GeV), assuming a standard dark matter halo. The XENON bounds depend on the scintillation efficiency factor L(eff) for which there is considerable uncertainty. Thus we consider various extrapolations for L(eff) at low energy. With the L(eff) measurements we consider, XENON100 results are found to be insensitive to the low-energy extrapolation. We find the strongest bounds are from XENON10, rather than XENON100, due to the lower energy threshold. For reasonable choices of L(eff) and for the case of SI elastic scattering, XENON10 is incompatible with the DAMA/LIBRA 3 sigma region and severely constrains the 7-12 GeV WIMP mass region of interest published by the CoGeNT Collaboration.
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| 6. |
- Scaffidi, Andre, et al.
(författare)
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Gamma rays from muons from WIMPs : Implementation of radiative muon decays for dark matter analyses
- 2016
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Ingår i: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 93:11
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Tidskriftsartikel (refereegranskat)abstract
- Dark matter searches in gamma ray final states often make use of the fact that photons can be produced from final state muons. Modern Monte Carlo generators and dark matter codes include the effects of final state radiation from muons produced in the dark matter annihilation process itself, but neglect the O(1%) radiative correction that arises from the subsequent muon decay. After implementing this correction we demonstrate the effect that it can have on dark matter phenomenology by considering the case of dark matter annihilation to four muons via scalar mediator production. We first show that the AMS-02 positron excess can no longer easily be made consistent with this final state once the Fermi-LAT dwarf limits are calculated with the inclusion of radiative muon decays, and we next show that the Fermi-LAT galactic center gamma excess can be improved with this final state after inclusion of the same effect. We provide code and tables for the implementation of this effect in the popular dark matter code micrOMEGAs, providing a solution for any model producing final state muons.
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