796 research outputs found
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.
New physics from ultrahigh energy cosmic rays
Cosmic rays from outer space enter the atmosphere with energies of up to
10^{11} GeV. The initial particle or a secondary hadron inside the shower may
then interact with an air nucleon to produce nonstandard particles. In this
article we study the production of new physics by high energy cosmic rays,
focusing on the long-lived gluino of split-SUSY models and a WIMP working as
dark matter. We first deduce the total flux of hadron events at any depth in
the atmosphere, showing that secondary hadrons can not be neglected. Then we
use these results to find the flux of gluinos and WIMPs that reach the ground
after being produced inside air showers. We also evaluate the probability of
producing these exotic particles in a single proton shower of ultrahigh energy.
Finally we discuss the possible signal in current and projected experiments.
While the tiny flux of WIMPs does not seem to have any phenomenological
consequences, we show that the gluinos could modify substantially the profile
of a small fraction of extensive air showers. In particular, they could produce
a distinct signal observable at AUGER in showers of large zenith angle.Comment: 9 pages, version to appear in PR
Cosmic Ray in the Northern Hemisphere: Results from the Telescope Array Experiment
The Telescope Array (TA) is the largest ultrahigh energy (UHE) cosmic ray
observatory in the northern hemisphere TA is a hybrid experiment with a unique
combination of fluorescence detectors and a stand-alone surface array of
scintillation counters. We will present the spectrum measured by the surface
array alone, along with those measured by the fluorescence detectors in
monocular, hybrid, and stereo mode. The composition results from stereo TA data
will be discussed. Our report will also include results from the search for
correlations between the pointing directions of cosmic rays, seen by the TA
surface array, with active galactic nuclei.Comment: 8 pages 11 figure, Proceedings of the APS Division of Particle and
Fields (DPF) Meeting, Aug 2011, Brown University, Providence, RI, US
Comment on "Correlation between Compact Radio Lout Quasars and Ultrahigh Energy Cosmic Rays"
In a recent paper, Farrar and Biermann argue that there is a strong
correlation between the direction of the five highest-energy cosmic-ray events
and compact, radio-loud quasars. This Comment shows that this analysis contains
several inconsistencies and errors so that the significance of any such
correlation is certainly greatly overestimated and perhaps nonexistent.Comment: 2 pages, REVTE
A Macroscopic Description of Coherent Geo-Magnetic Radiation from Cosmic Ray Air Showers
We have developed a macroscopic description of coherent electro-magnetic
radiation from air showers initiated by ultra-high energy cosmic rays due to
the presence of the geo-magnetic field. This description offers a simple and
direct insight in the relation between the properties of the air shower and the
time-structure of the radio pulse.Comment: 10 pages, 8 figures; submitted to Astroparticle Physic
Superheavy Dark Matter with Discrete Gauge Symmetries
We show that there are discrete gauge symmetries protect naturally heavy X
particles from decaying into the ordinary light particles in the supersymmetric
standard model. This makes the proposal very attractive that the superheavy X
particles constitute a part of the dark matter in the present universe. It is
more interesting that there are a class of discrete gauge symmetries which
naturally accommodate a long-lived unstable X particle. We find that in some
discrete Z_{10} models, for example, a superheavy X particle has lifetime
\tau_X \simeq 10^{11}-10^{26} years for its mass M_X \simeq 10^{13}-10^{14}
GeV. This long lifetime is guaranteed by the absence of lower dimensional
operators (of light particles) couple to the X. We briefly discuss a possible
explanation for the recently observed ultra-high-energy cosmic ray events by
the decay of this unstable X particle.Comment: 9 pages, Late
Susy QCD and High Energy Cosmic Rays 1. Fragmentation functions of Susy QCD
The supersymmetric evolution of the fragmentation functions (or timelike
evolution) within N=1 is discussed and predictions for the fragmentation
functions of the theory (into final protons) are given. We use a backward
running of the supersymmetric DGLAP equations, using a method developed in
previous works. We start from the usual QCD parameterizations at low energy and
run the DGLAP back, up to an intermediate scale -assumed to be supersymmetric-
where we switch-on supersymmetry. From there on we assume the applicability of
an N=1 supersymmetric evolution (ESAP). We elaborate on possible application of
these results to High Energy Cosmic Rays near the GZK cutoff.Comment: 36 pages, 12 fig
BL Lacertae are probable sources of the observed ultra-high energy cosmic rays
We calculate angular correlation function between ultra-high energy cosmic
rays (UHECR) observed by Yakutsk and AGASA experiments, and most powerful BL
Lacertae objects. We find significant correlations which correspond to the
probability of statistical fluctuation less than , including penatly
for selecting the subset of brightest BL Lacs. We conclude that some of BL Lacs
are sources of the observed UHECR and present a list of most probable
candidates.Comment: Replaced with the version accepted for publication in JETP Let
Possible Signature of Low Scale Gravity in Ultra High Enegry Cosmic Rays
We show that the existence of low scale gravity at TeV scale could lead to a
direct production of photons with energies above 10^22 eV due to annihilation
of ultra high energy neutrinos on relic massive neutrinos of the galactic halo.
Air showers initialized in the terrestrial atmosphere by these ultra energetic
photons could be collected in near future by the new generation of cosmic ray
experiments.Comment: 5 pages, 3 figure
On the Single-Zone Modeling for Optimal Climate Control of a Real-Sized Livestock Stable System
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