In the present paper, it is assumed that there exist two dark matter particles: superheavy dark matter particles (SHDM), whose mass ∼ inflaton mass, and lighter fermion dark matter particles (LFDM) ...which are the ultra-relativistic products of its decay. The event rates of LFDM measured by the Pierre Auger observatory (Auger) are evaluated in the energy range between 1 EeV and 1 ZeV at the zenith angles between 0°and 60°when the different lifetimes of decay of SHDM. Thus it is proved that the possibility of measurement of these LFDM at Auger. Based on the assumption that the detection efficiency for a shower caused by LFDM is set to be 100%, the LFDM contribution to the energy spectrum of extreme energy cosmic rays (EECRs) is discussed. And it is found that there are some hints on the existence of SHDM and LFDM in the past EECRs observations.
We report on the simulation studies addressing the possibility of dark matter particle (DMP) decaying into
μ
+
μ
−
channel. While not much is known about the properties of dark matter particles ...except through their gravitational effect, it has been recently conjectured that the so-called ‘anomalous Kolar events’ observed some decades ago may be due to the decay of unstable dark matter particles. The aim of this study is to see if this conjecture can be verified at the proposed iron calorimeter (ICAL) detector at INO. We study the possible decay to
μ
±
mode which may be seen in this detector with some modifications. For the purposes of simulation, we assume that the channel saturates the decay width for the mass ranging from 1 to 50 GeV/c
2
. The aim is not only to investigate the decay signatures, but also, more generally, to establish lower bounds on the lifetime of DMP even if no such decay takes place.
This volume is a compilation of the lectures at TASI 2011, held in Boulder, Colorado, June 2011. They cover topics in theoretical particle physics including the Standard Model and beyond, collider ...physics, dark matter, and cosmology, at a level intended to be accessible to students at the initial stages of their research careers.
The objective of the workshop series "The Identification of Dark Matter" is to assess critically the status of work attempting to identify what constitutes dark matter; in particular, to consider ...what techniques are currently being used, how successful they are, and what new techniques are likely to improve the prospects for identifying dark matter candidates in the future. This proceedings volume includes reviews on major particle astrophysics topics in the field of dark matter, as well as short contributed papers.
Ultra compact dwarf galaxies (UCDs) have similar properties as massive globular clusters or the nuclei of nucleated galaxies. Recent observations suggesting a high dark matter content and a steep ...spatial distribution within groups and clusters provide new clues as to their origins. We perform high-resolution N-body/smoothed particle hydrodynamics simulations designed to elucidate two possible formation mechanisms for these systems: the merging of globular clusters in the centre of a dark matter halo, or the massively stripped remnant of a nucleated galaxy. Both models produce density profiles as well as the half light radii that can fit the observational constraints. However, we show that the first scenario results to UCDs that are underluminous and contain no dark matter. This is because the sinking process ejects most of the dark matter particles from the halo centre. Stripped nuclei give a more promising explanation, especially if the nuclei form via the sinking of gas, funneled down inner galactic bars, since this process enhances the central dark matter content. Even when the entire disk is tidally stripped away, the nucleus stays intact and can remain dark matter dominated even after severe stripping. Total galaxy disruption beyond the nuclei only occurs on certain orbits and depends on the amount of dissipation during nuclei formation. By comparing the total disruption of CDM subhaloes in a cluster potential we demonstrate that this model also leads to the observed spatial distribution of UCDs which can be tested in more detail with larger data sets.
We study the internal structure of galactic size dark matter halos in the standard ΛCold Dark Matter model under the assumption that cold dark matter consists of light neutralinos whose annihilation ...cross section is large.We use high resolution cosmological hydrodynamic simulations which include radiative cooling, starformation and supernova feedback effects. We show that the dissipative processes generally act as steepening the dark matter density profile, whereas supernova feedback mitigates the effect. However, when all of the processes are included, we still find many subhalos that have a steep (αr–1.5–2) density profiles. Such subhalos may be bright sources of γ-ray via pair-annihilation of neutralinos. We also find poor correlation between the stellar velocity dispersion profile and the underlying dark matter density profiles of subhalos. Observations of stellar velocity dispersions need to be interpreted with caution.
Blazars produce a large fraction of the observed extragalactic gamma ray background between 100 MeV and 100 GeV. The average spectrum of the resolved blazars in the 3rd EGRET catalogue is too steep ...to be consistent with the shape of the background spectrum above 1 GeV. The most proliferant emitters above 100 GeV, the high-peaked blazars, which are too faint to have been detected with EGRET, but of which an increasing number is now being detected with imaging air Cherenkov telescopes such as MAGIC, H.E.S.S., and VERITAS, could supply a substantial contribution to the background above GeV energies. We show that dark matter annihilation in clumpy halos could naturally produce an emission component peaking at ~20 GeV. Adding this to the blazar-origin component, a best-fit model for the extragalactic gamma ray background is obtained.
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\begin{document}$b\to s+$\end{document}nothing, as a probe of light Dark Matter (DM).
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