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M. Cirellia, M. Kadastikb, M. Raidalb, A. Strumiac
Taking into account spins, we classify all two-body non-relativistic Dark Matter annihilation channels to the allowed polarization states of Standard Model particles, computing the energy spectra of the stable final-state particles relevant for indirect DM detection. We study the DM masses, annihilation channels and cross sections that can reproduce the PAMELA indications of an e+ excess consistently with the PAMELA View the MathML source data and the ATIC/PPB-BETS e++e− data. From the PAMELA data alone, two solutions emerge: (i) either the DM particles that annihilate into W,Z,h must be heavier than about 10 TeV or (ii) the DM must annihilate only into leptons. Thus in both cases a DM particle compatible with the PAMELA excess seems to have quite unexpected properties. The solution (ii) implies a peak in the e++e− energy spectrum, which, indeed, seems to appear in the ATIC/PPB-BETS data around 700 GeV. If upcoming data from ATIC-4 and GLAST confirm this feature, this would point to a O(1) TeV DM annihilating only into leptons. Otherwise the solution (i) would be favored. We comment on the implications of these results for DM models, direct DM detection and colliders as well as on the possibility of an astrophysical origin of the excess.
Links : http://www.sciencedirect.com/science/article/pii/S0550321308006627
How the Self-Interacting Dark Matter Model Explains the Diverse Galactic Rotation Curves
Ayuki Kamada, Manoj Kaplinghat, Andrew B. Pace, Hai-Bo Yu
The rotation curves of spiral galaxies exhibit a diversity that has been difficult to understand in the cold dark matter (CDM) paradigm. We show that the self-interacting dark matter (SIDM) model provides excellent fits to the rotation curves of a sample of galaxies with asymptotic velocities in the 25 to 300 km/s range that exemplify the full range of diversity. We only assume the halo concentration-mass relation predicted by the CDM model and a fixed value of the self-interaction cross section.In dark matter dominated galaxies, thermalization due to self-interactions creates large cores and reduces dark matter densities. In contrast, thermalization leads to denser and smaller cores in more luminous galaxies, and naturally explains the flat rotation curves of the highly luminous galaxies. Our results demonstrate that the impact of the baryons on the SIDM halo profile and the scatter from the assembly history of halos as encoded in the concentration-mass relation can explain the diverse rotation curves of spiral galaxies.
Links : https://arxiv.org/abs/1611.02716
H.E.S.S. Collaboration: H. Abdallah, A. Abramowski, F. Aharonian, F. Ait Benkhali, A.G. Akhperjanian, E. Angüner, M. Arrieta, P. Aubert, M. Backes, A. Balzer, M. Barnard, Y. Becherini, J. Becker Tjus, D. Berge, S. Bernhard, K. Bernlöhr, E. Birsin, R. Blackwell, M. Böttcher, C. Boisson, J. Bolmont, P. Bordas, J. Bregeon, F. Brun, P. Brun, M. Bryan, T. Bulik, M. Capasso, J. Carr, S. Casanova, P.M. Chadwick, N. Chakraborty, R. Chalme-Calvet, R.C.G. Chaves, A. Chen, J. Chevalier, M. Chrétien, S. Colafrancesco, G. Cologna, B. Condon, J. Conrad, C. Couturier, Y. Cui, I.D. Davids, B. Degrange, C. Deil, P. deWilt, H.J. Dickinson, A. Djannati-Ataï, W. Domainko, A. Donath, L.O'C. Drury, G. Dubus, K. Dutson, J. Dyks, M. Dyrda, T. Edwards, K. Egberts, P. Eger, J.-P. Ernenwein, et al. (186 additional authors not shown)
The inner region of the Milky Way halo harbors a large amount of dark matter (DM). Given its proximity, it is one of the most promising targets to look for DM. We report on a search for the annihilations of DM particles using γ-ray observations towards the inner 300 parsecs of the Milky Way, with the H.E.S.S. array of ground-based Cherenkov telescopes. The analysis is based on a 2D maximum likelihood method using Galactic center (GC) data accumulated by H.E.S.S. over the last 10 years (2004-2014), and does not show any significant γ-ray signal above background. Assuming Einasto and Navarro-Frenk-White DM density profiles at the GC, we derive upper limits on the annihilation cross section ⟨σv⟩. These constraints are the strongest obtained so far in the TeV DM mass range and improve upon previous limits by a factor 5. For the Einasto profile, the constraints reach ⟨σv⟩ values of 6×10−26cm3s−1 in the W+W− channel for a DM particle mass of 1.5 TeV, and 2×10−26cm3s−1 in the τ+τ− channel for 1 TeV mass. For the first time, ground-based γ-ray observations have reached sufficient sensitivity to probe ⟨σv⟩ values expected from the thermal relic density for TeV DM particle
Links : https://arxiv.org/abs/1607.08142
The Doppler effect on indirect detection of dark matter using dark matter only simulations
Devon Powell, Ranjan Laha, Kenny C. Y. Ng, Tom Abel
Indirect detection of dark matter is a major avenue for discovery. However, baryonic backgrounds are diverse enough to mimic many possible signatures of dark matter. In this work, we study the newly proposed technique of dark matter velocity spectroscopy [Speckhard etal. PRL 2016 this https URL]. The non-rotating dark matter halo and the Solar motion produce a distinct longitudinal dependence of the signal which is opposite in direction to that produced by baryons. Using collisionless dark matter only simulations of Milky Way like halos, we show that this new signature is robust and holds great promise. We develop mock observations by high energy resolution X-ray spectrometer on a sounding rocket, the Micro-X experiment, to our test case, the 3.5 keV line. We show that by using six different pointings, Micro-X can exclude a constant line energy over various longitudes at ≥ 3σ. The halo triaxiality is an important effect and it will typically reduce the significance of this signal. We emphasize that this new smokingguninmotion signature of dark matter is general, and is applicable to any dark matter candidate which produces a sharp photon feature in annihilation or decay.
Links : https://arxiv.org/abs/1611.02714
First direct detection constraints on eV-scale hidden-photon dark matter with DAMIC at SNOLAB
A. Aguilar-Arevalo, D. Amidei, X. Bertou, M. Butner, G. Cancelo, A. Castañeda Vázquez, B.A. Cervantes Vergara, A.E. Chavarria, C.R. Chavez, J.R.T. de Mello Neto, J.C. D'Olivo, J. Estrada, G. Fernandez Moroni, R. Gaïor, Y. Guardincerri, K.P. Hernández Torres, F. Izraelevitch, A. Kavner, B. Kilminster, I. Lawson, A. Letessier-Selvon, J. Liao, A. Matalon, V.B.B. Mello, J. Molina, P. Privitera, K. Ramanathan, Y. Sarkis, T. Schwarz, M. Settimo, M. Sofo Haro, R. Thomas, J. Tiffenberg, E. Tiouchichine, D. Torres Machado, F. Trillaud, X. You, J. Zhou
We present direct detection constraints on the absorption of hidden-photon dark matter with particle masses in the range 1.2-30 eVc−2 with the DAMIC experiment at SNOLAB. Under the assumption that the local dark matter is entirely constituted of hidden photons, the sensitivity to the kinetic mixing parameter κ is competitive with constraints from solar emission, reaching a minimum value of 2.2×10−14 at 17 eVc−2. These results are the most stringent direct detection constraints on hidden-photon dark matter with masses 3-12 eVc−2 and the first demonstration of direct experimental sensitivity to ionization signals <12 eV from dark matter interactions.
Links : https://arxiv.org/abs/1611.03066
Final Results of the PICASSO Dark Matter Search Experiment
E. Behnke, M. Besnier, P. Bhattacharjee, X. Dai, M. Das, A. Davour, F. Debris, N. Dhungana, J. Farine, M. Fines-Neuschild, S. Gagnebin, G. Giroux, E. Grace, C.M. Jackson, A. Kamaha, C. B. Krauss, M. Lafrenière, M. Laurin, I. Lawson, L. Lessard, I. Levine, D. Marlisov, J.-P. Martin, P. Mitra, A.J. Noble, A. Plante, R. Podviyanuk, S. Pospisil, O. Scallon, S. Seth, N. Starinski, I. Stekl, U. Wichoski, V. Zacek
The PICASSO dark matter search experiment operated an array of 32 superheated droplet detectors containing 3.2 kg of C4F10 and collected an exposure of 231.4 kg days at SNOLAB between March 2012 and January 2014. We report on the final results of this experiment which includes for the first time the complete data set and improved analysis techniques including acoustic localization to allow fiducialization and removal of higher activity regions within the detectors. No signal consistent with dark matter was observed. We set limits for spin-dependent interactions on protons of σSDp = 1.32 × 10−2 pb (90% C.L.) at a WIMP mass of 20 GeV/c2. In the spin-independent sector we exclude cross sections larger than σSIp = 4.86 × 10−5 pb (90% C.L.) in the region around 7 GeV/c2. The pioneering efforts of the PICASSO experiment have paved the way forward for a next generation detector incorporating much of this technology and experience into larger mass bubble chambers
Links : https://arxiv.org/abs/1611.01499
Hyungjin Kim, Jeong-Pyong Hong, Chang Sub Shin
We study the effect of the elastic scattering on the non-thermally produced WIMP dark matter and its phenomenological consequences. The non-thermal WIMP becomes important when the reheating temperature is well below the freeze-out temperature. In the usual paradigm, the produced high energetic dark matter particles are quickly thermalized due to the elastic scattering with background radiations. The relic abundance is determined by the thermally averaged annihilation cross-section times velocity at the reheating temperature. In the opposite limit, the initial abundance is too small for the dark matter to annihilate so that the relic density is determined by the branching fraction of the heavy particle. We study the regions between these two limits, and show that the relic density depends not only on the annihilation rate, but also on the elastic scattering rate. Especially, the relic abundance of the p-wave annihilating dark matter crucially relies on the elastic scattering rate because the annihilation cross-section is sensitive to the dark matter velocity. We categorize the parameter space into several regions where each region has distinctive mechanism for determining the relic abundance of the dark matter at the present Universe. The consequence on the (in)direct detection is also studied
Links : https://arxiv.org/abs/1611.02287
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