1,759 research outputs found
A Faraway Quasar in the Direction of the Highest Energy Auger Event
The highest energy cosmic ray event reported by the Auger Observatory has an
energy of 148 EeV. It does not correlate with any nearby (z0.024) object
capable of originating such a high energy event. Intrigued by the fact that the
highest energy event ever recorded (by the Fly's Eye collaboration) points to a
faraway quasar with very high radio luminosity and large Faraday rotation
measurement, we have searched for a similar source for the Auger event. We find
that the Auger highest energy event points to a quasar with similar
characteristics to the one correlated to the Fly's Eye event. We also find the
same kind of correlation for one of the highest energy AGASA events. We
conclude that so far these types of quasars are the best source candidates for
both Auger and Fly's Eye highest energy events. We discuss a few exotic
candidates that could reach us from gigaparsec distances.Comment: 13 pages (version to be published in JCAP
Closing the Window on Strongly Interacting Dark Matter with IceCube
We use the recent results on dark matter searches of the 22-string IceCube
detector to probe the remaining allowed window for strongly interacting dark
matter in the mass range 10^4<m_X<10^15 GeV. We calculate the expected signal
in the 22-string IceCube detector from the annihilation ofsuch particles
captured in the Sun and compare it to the detected background. As a result, the
remaining allowed region in the mass versus cross sectionparameter space is
ruled out. We also show the expected sensitivity of the complete IceCube
detector with 86 strings.Comment: 5 pages, 7 figures. Uppdated figures 2 and 3 (y-axis normalization
and label) . Version accepted for publication in PR
Detection of Exotic Massive Hadrons in Ultra High Energy Cosmic Ray Telescopes
We investigate the detection of exotic massive strongly interacting hadrons
(uhecrons) in ultra high energy cosmic ray telescopes. The conclusion is that
experiments such as the Pierre Auger Observatory have the potential to detect
these particles. It is shown that uhecron showers have clear distinctive
features when compared to proton and nuclear showers. The simulation of uhecron
air showers, and its detection and reconstruction by fluorescence telescopes is
described. We determine basic cuts in observables that will separate uhecrons
from the cosmic ray bulk, assuming this is composed by protons. If these are
composed by heavier nucleus the separation will be much improved. We also
discuss photon induced showers. The complementarity between uhecron detection
in accelerator experiments is discussed.Comment: 9 page 9 figure
Análise cariológica e molecular de Proechimys Allen, 1899 (Rodentia, Echimyidae) da região Amazônica
Karyologic and molecular analyses were carried out in Proechimys quadruplicatus and two other Proechimys species from the northern bank of the Rio Negro, Brazil. Analyses of cytb DNA sequence data and karyologic attributes partially sustained the goeldii species group. Molecular analyses grouped the two Proechimys sp. A haplotypes here sequenced with other specimens from the Amazonian region of Brazil and Venezuela, suggesting that they belonged to a single taxon. The three specimens of Proechimys sp. B also formed a monophyletic group. Proechimys sp. A,Proechimys sp. B, and P. guyannensis were grouped by karyologic and/or molecular data indicating that they are very similar one another and belong to the same species group, the guyannensis group. Phylogeographic analyses showed a high geographic structuration in the Proechimys sp. A population and the presence of a median vector between haplotypes of different rivers suggested that the large Amazonian rivers are barrier to these population.Análises cariológicas e moleculares foram realizadas em Proechimys quadruplicatus e duas outras espécies de Proechimys da margem norte do rio Negro, Brasil. Análises da seqüência de ADN do citocromo b e dos atributos cariológicos sustentam parcialmente o grupo de espécies goeldii. As análises moleculares agruparam os dois haplótipos de Proechimys sp. A aqui seqüenciados com outros espécimes da região Amazônica do Brasil e Venezuela sugerindo que eles pertençam ao mesmo táxon. Os três espécimes de Proechimys sp. B formam um grupo monofilético. Proechimys sp. A, Proechimys sp. B e P. guyannensis se agrupam pelos dados moleculares e/ou cariológicos indicando que eles são bastantes similares e pertencem ao mesmo grupo de espécies, o grupoguyannenis. A análise filogeográfica mostrou um padrão de estruturação geográfica forte nas populações de Proechimys sp. A, e a presença de vetores médios entre os haplótipos de diferentes rios, na análise de “median - joining”, sugere que estes rios sejam barreiras para estas populações
Neutrino Telescopes as a Direct Probe of Supersymmetry Breaking
We consider supersymmetric models where the scale of supersymmetry breaking
lies between 5 GeV and 5 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 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
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