982 research outputs found
Muons in gamma showers
Muon production in gamma-induced air showers, accounting for all major processes. For muon energies in the GeV region the photoproduction is by far the most important process, while the contribution of micron + micron pair creation is not negligible for TeV muons. The total rate of muons in gamma showers is, however, very low
The Greisen Equation Explained and Improved
Analytic description of the evolution of cosmic ray showers is dominated by
the Greisen equation nearly five decades old. We present an alternative
approach with several advantages. Among the new features are a prediction of
the differential distribution, replacing Greisen's form which fails to be
positive definite. Explicit comparison with Monte Carlo simulations shows
excellent agreement after a few radiation lengths of development. We find a
clear connection between Monte Carlo adjustment of Greisen's form and
underlying physics, and present a concise derivation with all steps explicit.
We also reconstruct the steps needed to reproduce Greisen's approximate
formula, which appears not to have been published previously.Comment: 8 pages, 7 figures, revised version, accepted for publication in
Phys. Rev.
Active Galactic Nuclei with Starbursts: Sources for Ultra High Energy Cosmic Rays
Ultra high energy cosmic ray events presently show a spectrum, which we
interpret here as galactic cosmic rays due to a starburst in the radio galaxy
Cen A pushed up in energy by the shock of a relativistic jet. The knee feature
and the particles with energy immediately higher in galactic cosmic rays then
turn into the bulk of ultra high energy cosmic rays. This entails that all
ultra high energy cosmic rays are heavy nuclei. This picture is viable if the
majority of the observed ultra high energy events come from the radio galaxy
Cen A, and are scattered by intergalactic magnetic fields across most of the
sky.Comment: 4 pages, 1 figure, proceedings of "High-Energy Gamma-rays and
Neutrinos from Extra-Galactic Sources", Heidelber
The nature of the highest energy cosmic rays
Ultra high energy gamma rays produce electron--positron pairs in interactions
on the geomagnetic field. The pair electrons suffer magnetic bremsstrahlung and
the energy of the primary gamma ray is shared by a bunch of lower energy
secondaries. These processes reflect the structure of the geomagnetic field and
cause experimentally observable effects. The study of these effects with future
giant air shower arrays can identify the nature of the highest energy cosmic
rays as either gamma-rays or nuclei.Comment: 15 pages of RevTeX plus 6 postscript figures, tarred, gzipped and
uuencoded. Subm. to Physical Review
Limits on models of the ultrahigh energy cosmic rays based on topological defects
An erratum exists for this article. Please see the description link below for details.Using the propagation of ultrahigh energy nucleons, photons, and electrons in the universal radiation backgrounds, we obtain limits on the luminosity of topological defect scenarios for the origin of the highest energy cosmic rays. The limits are set as a function of the mass of the X particles emitted by the cosmic strings or other defects, the cosmological evolution of the topological defects, and the strength of the extragalactic magnetic fields. The existing data on the cosmic ray spectrum and on the isotropic 100 MeV gamma-ray background limit significantly the parameter space in which topological defects can generate the flux of the highest energy cosmic rays, and rule out models with the standard X-particle mass of 10¹⁶GeV and higher.R. J. Protheroe and Todor Stane
A three-dimensional calculation of atmospheric neutrinos
A Monte-Carlo calculation of the atmospheric neutrino fluxes [1,2] has been
extended to take account of the three-dimensional (3D) nature of the problem,
including the bending of secondary particles in the geomagnetic field. Emphasis
has been placed on minimizing the approximations when introducing the 3D
considerations. In this paper, we describe the techniques used and quantify the
effects of the small approximations which remain. We compare 3D and 1D
calculations using the same physics input in order to evaluate the conditions
under which the 3D calculation is required and when the considerably simpler 1D
calculation is adequate. We find that the 1D and 3D results are essentially
identical for neutrino energy greater than 5 GeV except for small effects in
the azimuthal distributions due to bending of the secondary muon by the
geomagnetic field during their propagation in the atmosphere.Comment: 24 pages, 15 figures, LaTeX, to be submitted to Physical Review
Charged Higgs boson contribution to for very large in the two Higgs doublet model with UHE-neutrinos
We study the deep inelastic process
(with an isoscalar nucleon), in the context of the
two Higgs doublet model {\it type two} (2HDM(II)). In particular, we discuss
the contribution to the total cross section of diagrams, in which a charged
Higgs boson is exchanged. We show that for large values of such
contribution for an inclusive dispersion generated through the collision of an
ultrahigh energy tau-neutrino on a target nucleon can reach up to 57% of the
value of the contribution of the exchange diagrams (i.e. can reach up to
57% of the standard model (SM) prediction) and could permit to distinguish
between the SM and the 2HDM(II) predictions at the Pierre Auger Observatory.Comment: 10 pages, 5 figure
Oscillations of solar atmosphere neutrinos
The Sun is a source of high energy neutrinos (E > 10 GeV) produced by cosmic
ray interactions in the solar atmosphere. We study the impact of three-flavor
oscillations (in vacuum and in matter) on solar atmosphere neutrinos, and
calculate their observable fluxes at Earth, as well as their event rates in a
kilometer-scale detector in water or ice. We find that peculiar three-flavor
oscillation effects in matter, which can occur in the energy range probed by
solar atmosphere neutrinos, are significantly suppressed by averaging over the
production region and over the neutrino and antineutrino components. In
particular, we find that the relation between the neutrino fluxes at the Sun
and at the Earth can be approximately expressed in terms of phase-averaged
``vacuum'' oscillations, dominated by a single mixing parameter (the angle
theta_23).Comment: v2: 11 pages, 8 eps figures. Content added (Sec. III D and Fig. 6),
references updated. Matches the published versio
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