1,502 research outputs found
Limiting SUSY-QCD spectrum and its application for decays of superheavy particles
The supersymmetric generalization of the limiting and Gaussian QCD spectra is
obtained. These spectra are valid for , when the main contribution to
the parton cascade is given by gluons and gluinos. The derived spectra are
applied to decaying superheavy particles with masses up to the GUT scale. These
particles can be relics from the Big Bang or produced by topological defects
and could give rise to the observed ultrahigh energy cosmic rays. General
formulae for the fluxes of protons, photons and neutrinos due to decays of
superheavy particles are obtained.Comment: 8 pages, revtex, 3 ps figures. v2 minor changes, v3 typo in eq.(15)
corrected; version to appear in Phys. Lett.
SuperGZK neutrinos: testing physics beyond the Standard Model
The sources and fluxes of superGZK neutrinos, eV, are discussed.
The most promising sources are reionization bright phase, topological defects,
superheavy dark matter and mirror matter. The energy of neutrinos can be above
the GUT scale ( GeV). The predicted fluxes are observable by
future space detectors EUSO and OWL.Comment: JD talk at XXI Texas Symposium (Florence
Ultra High Energy Cosmic Rays: The disappointing model
We develop a model for explaining the data of Pierre Auger Observatory
(Auger) for Ultra High Energy Cosmic Rays (UHECR), in particular, the mass
composition being steadily heavier with increasing energy from 3 EeV to 35 EeV.
The model is based on the proton-dominated composition in the energy range (1 -
3) EeV observed in both Auger and HiRes experiments. Assuming extragalactic
origin of this component, we argue that it must disappear at higher energies
due to a low maximum energy of acceleration, E_p^{\max} \sim (4 - 10) EeV.
Under an assumption of rigidity acceleration mechanism, the maximum
acceleration energy for a nucleus with the charge number Z is ZE_p^{\max}, and
the highest energy in the spectrum, reached by Iron, does not exceed (100 -
200) EeV. The growth of atomic weight with energy, observed in Auger, is
provided by the rigidity mechanism of acceleration, since at each energy
E=ZE_p^{\max} the contribution of nuclei with Z' < Z vanishes. The described
model has disappointing consequences for future observations in UHECR: Since
average energies per nucleon for all nuclei are less than (2 - 4) EeV, (i) pion
photo-production on CMB photons in extragalactic space is absent; (ii) GZK
cutoff in the spectrum does not exist; (iii) cosmogenic neutrinos produced on
CMBR are absent; (iv) fluxes of cosmogenic neutrinos produced on infrared -
optical background radiation are too low for registration by existing detectors
and projects. Due to nuclei deflection in galactic magnetic fields, the
correlation with nearby sources is absent even at highest energies.Comment: Essentially revised version as published in Astropart. Physics 10
pages, 6 figure
Ultra High Energy Cosmic Rays: Anisotropies and Spectrum
The recent results of the Pierre Auger Observatory on the possible
correlation of Ultra High Energy Cosmic Rays events and several nearby discrete
sources could be the starting point of a new era with charged particles
astronomy. In this paper we introduce a simple model to determine the effects
of any local distribution of sources on the expected flux. We consider two
populations of sources: faraway sources uniformly distributed and local point
sources. We study the effects on the expected flux of the local distribution of
sources, referring also to the set of astrophysical objects whose correlation
with the Auger events is experimentally claimed.Comment: 17 pages, 13 eps figures, version accepted for publication in
Astroparticle Physic
Hidden source of high-energy neutrinos in collapsing galactic nucleus
We propose the model of a short-lived very powerful source of high energy
neutrinos. It is formed as a result of the dynamical evolution of a galactic
nucleus prior to its collapse into a massive black hole and formation of
high-luminosity AGN. This stage can be referred to as ``pre-AGN''. A dense
central stellar cluster in the galactic nucleus on the late stage of evolution
consists of compact stars (neutron stars and stellar mass black holes). This
cluster is sunk deep into massive gas envelope produced by destructive
collisions of a primary stellar population. Frequent collisions of neutron
stars in a central stellar cluster are accompanied by the generation of
ultrarelativistic fireballs and shock waves. These repeating fireballs result
in a formation of the expanding rarefied cavity inside the envelope. The
charged particles are effectively accelerated in the cavity and, due to
pp-collisions in the gas envelope, they produce high energy neutrinos. All high
energy particles, except neutrinos, are absorbed in the thick envelope.
Duration of this pre-AGN phase is about 10 yr, the number of the sources can be
\~ 10 per cosmological horizon. High energy neutrino signal can be detected by
underground neutrino telescope with effective area ~1 km^2.Comment: small changes, to be published in Astroparticle Physic
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