Consequences of short range interactions between dark matter and protons in galaxy clusters

Protons gain energy in short range collisions with heavier dark matter particles (DMPs) of comparable velocity dispersion. We examine the conditions under which the heating of baryons by scattering off DMPs can offset radiative cooling in the cores of galaxy clusters. Collisions with a constant cross section independent of the relative velocity of the colliding particles, cannot produce stable thermal balance. In this case, avoiding an unrealistic increase of the central temperatures yields the upper bound on the cross-section, \sigma_xp<10^-25 cm^2 (m_x/m_p), where m_x and m_p are the DMP and proton mass, respectively. A stable balance, however, can be achieved for a power law dependence on the relative velocity, V, of the form \sigma_xp \propto V^a with a<-3. An advantage of this heating mechanism is that it preserves the metal gradients observed in clusters.Comment: 7 pages, new calculations include

On invariants of almost symplectic connections

We study the irreducible decomposition under Sp(2n, R) of the space of torsion tensors of almost symplectic connections. Then a description of all symplectic quadratic invariants of torsion-like tensors is given. When applied to a manifold M with an almost symplectic structure, these instruments give preliminary insight for finding a preferred linear almost symplectic connection on M . We rediscover Ph. Tondeur's Theorem on almost symplectic connections. Properties of torsion of the vectorial kind are deduced

Neutrino Telescopes as a Direct Probe of Supersymmetry Breaking

We consider supersymmetric models where the scale of supersymmetry breaking lies between 5 $\times 10^6$ GeV and 5 $\times 10^8$ GeV. In this class of theories, which includes models of gauge mediated supersymmetry breaking, the lightest supersymmetric particle is the gravitino. The next to lightest supersymmetric particle is typically a long lived charged slepton with a lifetime between a microsecond and a second, depending on its mass. Collisions of high energy neutrinos with nucleons in the earth can result in the production of a pair of these sleptons. Their very high boost means they typically decay outside the earth. We investigate the production of these particles by the diffuse flux of high energy neutrinos, and the potential for their observation in large ice or water Cerenkov detectors. The relatively small cross-section for the production of supersymmetric particles is partially compensated for by the very long range of heavy particles. The signal in the detector consists of two parallel charged tracks emerging from the earth about 100 meters apart, with very little background. A detailed calculation using the Waxman-Bahcall limit on the neutrino flux and realistic spectra shows that km$^3$ experiments could see as many as 4 events a year. We conclude that neutrino telescopes will complement collider searches in the determination of the supersymmetry breaking scale, and may even give the first evidence for supersymmetry at the weak scale.Comment: 4 pages, 3 figure

Astrophysical Neutrino Event Rates and Sensitivity for Neutrino Telescopes

Spectacular processes in astrophysical sites produce high-energy cosmic rays which are further accelerated by Fermi-shocks into a power-law spectrum. These, in passing through radiation fields and matter, produce neutrinos. Neutrino telescopes are designed with large detection volumes to observe such astrophysical sources. A large volume is necessary because the fluxes and cross-sections are small. We estimate various telescopes' sensitivities and expected event rates from astrophysical sources of high-energy neutrinos. We find that an ideal detector of km^2 incident area can be sensitive to a flux of neutrinos integrated over energy from 10^5 and 10^{7} GeV as low as 1.3 * 10^(-8) * E^(-2) (GeV/cm^2 s sr) which is three times smaller than the Waxman-Bachall conservative upper limit on potential neutrino flux. A real detector will have degraded performance. Detection from known point sources is possible but unlikely unless there is prior knowledge of the source location and neutrino arrival time.Comment: Section added +modification

The DarkSide project

DarkSide is a graded experimental project based on radiopure argon, and is now, and will be, used in direct dark matter searches. The present DarkSide-50 detector, operating at the Gran Sasso National Laboratory, is a dual-phase, 50 kg, liquid argon time-projection-chamber surrounded by an active liquid scintillator veto. It is designed to be background free in 3 years of operation. DS-50 performances, when filled with atmospheric argon, are reporte

Calagem e parcelamento da adubação fosfatada em porta-enxertos de seringueira.

bitstream/item/57409/1/Belem-BP6.pd

Cosmic-Ray Anisotropies in Right Ascension Measured by the Pierre Auger Observatory

We present measurements of the large-scale cosmic-ray (CR) anisotropies in R.A., using data collected by the surface detector array of the Pierre Auger Observatory over more than 14 yr. We determine the equatorial dipole component, ${{\boldsymbol{d}}}_{\perp }$, through a Fourier analysis in R.A. that includes weights for each event so as to account for the main detector-induced systematic effects. For the energies at which the trigger efficiency of the array is small, the "east–west" method is employed. Besides using the data from the array with detectors separated by 1500 m, we also include data from the smaller but denser subarray of detectors with 750 m separation, which allows us to extend the analysis down to ∼0.03 EeV. The most significant equatorial dipole amplitude obtained is that in the cumulative bin above 8 EeV, ${d}_{\perp }={6.0}_{-0.9}^{+1.0}$%, which is inconsistent with isotropy at the 6σ level. In the bins below 8 EeV, we obtain 99% CL upper bounds on d⊥ at the level of 1%–3%. At energies below 1 EeV, even though the amplitudes are not significant, the phases determined in most of the bins are not far from the R.A. of the Galactic center, at αGC = −94°, suggesting a predominantly Galactic origin for anisotropies at these energies. The reconstructed dipole phases in the energy bins above 4 EeV point instead to R.A. that are almost opposite to the Galactic center one, indicative of an extragalactic CR origin

The veto system of the DarkSide-50 experiment

Nuclear recoil events produced by neutron scatters form one of the most important classes of background in WIMP direct detection experiments, as they may produce nuclear recoils that look exactly like WIMP interactions. In DarkSide-50, we both actively suppress and measure the rate of neutron-induced background events using our neutron veto, composed of a boron-loaded liquid scintillator detector within a water Cherenkov detecto