354 research outputs found
Results from the Telescope Array and review of HiRes
A new measurement of the cosmic ray spectrum using the Telescope Array surface arrays is presented. Results on the composition of ultra-high energy cosmic rays from air-fluorescence measurements of shower maximum distributions are presented. Preliminary data from the Telescope Array experiment are compared with HiRes measurements as well as Pierre Auger Observatory results. Systematic errors are discussed. Preliminary results on large scale anisotropy are shown
The Unreasonable Effectiveness of the Air-Fluorescence Technique in Determining the EAS Shower Maximum
We review all existing air-fluorescence measurements of the elongation rate
of extensive air showers (slope of mean EAS shower maximum (Xmax) vs log of
shower energy E) above 1017 eV. We find remarkable agreement for all current
and historic experiments over a 30 year period for the energy range from 1017
to 3x1018 eV. The mean elongation rate in this energy interval is near 80
gm/cm2/decade Above this energy, experiments in the Northern hemisphere are in
good agreement with an average elongation rate of 48 +/- 10 gm/cm2/decade while
Southern hemisphere experiments have a flatter elongation rate of 26 +/- 2
gm/cm2/decade We point out that, given the agreement at lower energies,
possible systematic reasons for this difference are unlikely. Given this, the
world elongation rate data alone may indicate a composition difference of UHECR
in the Northern and Southern hemisphere and thus a diversity of UHECR sources
in the Northern and Southern sky.Comment: Accepted by JET
Search for new particles at the alternating-gradient-synchrotron beam dump
Journal ArticleThis paper presents results of a beam-dump experiment performed at the Brookhaven alternating-gradient synchrotron to search for prompt sources of neutrinos and axionlike particles. We observe no excess of vµ or events, and no excess in neutral-current events over that expected from neutrinos from ir and K decays. We report on limits of prompt particle-production cross sections and lifetimes
Effect of Clouds on Apertures of Space-based Air Fluorescence Detectors
Space-based ultra-high-energy cosmic ray detectors observe fluorescence light
from extensive air showers produced by these particles in the troposphere.
Clouds can scatter and absorb this light and produce systematic errors in
energy determination and spectrum normalization. We study the possibility of
using IR remote sensing data from MODIS and GOES satellites to delimit clear
areas of the atmosphere. The efficiency for detecting ultra-high-energy cosmic
rays whose showers do not intersect clouds is determined for real, night-time
cloud scenes. We use the MODIS SST cloud mask product to define clear pixels
for cloud scenes along the equator and use the OWL Monte Carlo to generate
showers in the cloud scenes. We find the efficiency for cloud-free showers with
closest approach of three pixels to a cloudy pixel is 6.5%, exclusive of other
factors. We conclude that defining a totally cloud-free aperture reduces the
sensitivity of space-based fluorescence detectors to unacceptably small levels.Comment: 24 pages, 8 Figure
Search for compact sources of cosmic photons above 200 TeV
Journal ArticleFrom April 1988 to February 1990 we used a two-level array of scintillators to search in the cosmic radiation for compact sources of y rays above 200 TeV. Counters on the surface measured the size and direction of extensive air showers while counters buried 3 m below ground measured their muon content. Showers induced by y rays are expected to have many fewer muons than those initiated by hadrons so the selection of muon-poor showers should greatly reduce the background of hadronic showers. Three objects, Cygnus X-3, the Crab nebula, and Hercules X-l, were examined in detail. Searches were made on short and long time scales and source periodicity was used, where applicable, to enhance any possible signals. We found no evidence for any compact sources
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