No abstract

No abstract

The DAMA/NaI and DAMA/LIBRA annual modulation data, which may be interpreted as a signal for the existence of weakly interacting dark matter (WIMPs) in our galactic halo, are examined in light of null results from other experiments: CDMS, XENON10, CRESST I, CoGeNT, TEXONO, and Super-Kamiokande (Su-perK). We use the energy spectrum of the combined DAMA modulation data given in 36 bins, and include the effect of channeling. Several statistical tools are implemented in our study: likelihood ratio with a global fit and with raster scans in the WIMP mass and goodness-of-fit (g.o.f.). These approaches allow us to differentiate between the preferred (global best fit) and allowed (g.o.f.) parameter regions. It is hard to find WIMP masses and couplings consistent with all existing data sets; the surviving regions of parameter space are found here. For spin-independent (SI) interactions, the best fit DAMA regions are ruled out to the 3σ C.L., even with channeling taken into account. However, for WIMP masses of ∼8 GeV some parameters outside these regions still yield a moderately reasonable fit to the DAMA data and are compatible with all 90% C.L. upper limits from negative searches, when channeling is included. For spin-dependent (SD) interactions with proton-only couplings, a range of masses below 10 GeV is compatible with DAMA and other experiments, with and without channeling, when SuperK indirect detection constraints are included; without the SuperK constraints, masses as high as ∼20 GeV are compatible. For SD neutron-only couplings we find no parameters compatible with all the experiments. Mixed SD couplings are examined: e.g. ∼8 GeV mass WIMPs with a n = ±a p are found to be consistent with all experiments. In short, there are surviving regions at low mass for both SI and SD interactions; if indirect detection limits are relaxed, some SD proton-only couplings at higher masses also survive.

No abstract

Editor: S. DodelsonWe report a measurement of the flux of cosmic rays with unprecedented precision and statistics using the Pierre Auger Observatory. Based on fluorescence observations in coincidence with at least one surface detector we derive a spectrum for energies above 10 18 eV. We also update the previously published energy spectrum obtained with the surface detector array. The two spectra are combined addressing the systematic uncertainties and, in particular, the influence of the energy resolution on the spectral shape. 242Pierre Auger Collaboration / Physics Letters B 685 (2010) The spectrum can be described by a broken power law E −γ with index γ = 3.3 below the ankle which is measured at log 10 (E ankle /eV) = 18.6. Above the ankle the spectrum is described by a power law with index 2.6 followed by a flux suppression, above about log 10 (E/eV) = 19.5, detected with high statistical significance.

If the energy density of the Universe before nucleosynthesis is dominated by a scalar field φ that decays and reheats the plasma to a temperature TRH smaller than the standard neutralino freeze out temperature, the neutralino relic density differs from its standard value. In this case, the relic density depends on two additional parameters: TRH, and the number of neutralinos produced per φ decay per unit mass of the φ field. In this paper, we numerically study the neutralino relic density as a function of these reheating parameters within minimal supersymmetric standard models and show that the dark matter constraint can almost always be satisfied. I. MOTIVATIONThe neutralino is considered a good dark matter candidate, one that naturally yields the required relic density. Recently, however, it has been recognized that, owing to the experimental constraints and to the increased precision in the determination of the dark matter content of the Universe, the agreement between the observed relic density, Ω cdm h 2 = 0.113 ± 0.009 [1] 1 and the relic density predicted with standard cosmological assumptions, is far from being a generic feature of supersymmetric models. In fact, models with bino-like neutralinos tend to overproduce them, and special mechanisms such as coannihilations or resonant annihilations are required to suppress the relic density down to the observed range. In contrast, models with higgsino-or wino-like neutralinos usually give too small a relic density and, to compensate for it, large neutralino masses (m χ > 1 TeV) are needed. Non-standard cosmologies and in particular models with low reheating temperatures provide a plausible solution to this problem. These include models with moduli decay [3], Q-ball decay [4], and thermal inflation [5]. In all of these models there is a late episode of entropy production and non-thermal production of the LSP in particle decays is possible.We concentrate on cosmological models in which the early Universe is dominated by the energy density of a scalar field that after some time decays giving rise to the radiation dominated era. The decay of the scalar field into light degrees of freedom and their subsequent thermalization -the reheating process-leaves the Universe at a temperature T RH known as the reheating temperature. If, as assumed in the standard scenario, T RH is larger than the neutralino freeze out temperature (T f.o. ≃ m χ /20), the neutralino relic density is insensitive to its value. But, because we have no physical evidence of the radiation dominated Universe before big-bang nucleosynthesis, T RH should be considered as a cosmological parameter that can take any value above a few MeV [6,7].The existence of a weakly coupled scalar field that dominates the Universe during the process of neutralino production and freeze out may affect the relic density in several ways. It modifies the temperature-scale factor and the temperature-expansion rate relations [8,9,10] that determine the freeze out condition. It dilutes the neutralino thermal abundance by incr...

Using data collected at the Pierre Auger Observatory during the past 3.7 years, we demonstrated a correlation between the arrival directions of cosmic rays with energy above 6 x 10(19) electron volts and the positions of active galactic nuclei (AGN) lying within approximately 75 megaparsecs. We rejected the hypothesis of an isotropic distribution of these cosmic rays with at least a 99% confidence level from a prescribed a priori test. The correlation we observed is compatible with the hypothesis that the highest-energy particles originate from nearby extragalactic sources whose flux has not been substantially reduced by interaction with the cosmic background radiation. AGN or objects having a similar spatial distribution are possible sources.

20 pages, 3 figures Submitted to Phys.Rev.Lett.International audienceThe surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming tau neutrinos that interact in Earth's crust. Tau leptons from ντ charged-current interactions can emerge and decay in the atmosphere to produce a nearly horizontal shower with a significant electromagnetic component. The data collected between 1 January 2004 and 31 August 2007 are used to place an upper limit on the diffuse flux of ντ at EeV energies. Assuming an Eν-2 differential energy spectrum the limit set at 90% C.L. is Eν2dNντ/dEν<1.3×10-7GeVcm-2s-1sr-1 in the energy range 2×1017e