55 research outputs found
Observation of the shadows of the moon and sun using 100 TeV cosmic rays
Journal ArticleThe Chicago Air Shower Array (CASA) is a large ground-based scintillation detector [1-4]. It is located at the Dugway Proving Ground is west central Utah, latitude 40°N and mean atmospheric depth 870 g / c m 2. A schematic aerial view of CASA is shown in Fig. 1. Each dot represents one scintillation station of the array
Exploration of a 100 TeV gamma-ray northern sky using the Tibet air-shower array combined with an underground water-Cherenkov muon-detector array
Aiming to observe cosmic gamma rays in the 10 - 1000 TeV energy region, we
propose a 10000 m^2 underground water-Cherenkov muon-detector (MD) array that
operates in conjunction with the Tibet air-shower (AS) array. Significant
improvement is expected in the sensitivity of the Tibet AS array towards
celestial gamma-ray signals above 10 TeV by utilizing the fact that
gamma-ray-induced air showers contain far fewer muons compared with
cosmic-ray-induced ones. We carried out detailed Monte Carlo simulations to
assess the attainable sensitivity of the Tibet AS+MD array towards celestial
TeV gamma-ray signals. Based on the simulation results, the Tibet AS+MD array
will be able to reject 99.99% of background events at 100 TeV, with 83% of
gamma-ray events remaining. The sensitivity of the Tibet AS+MD array will be
~20 times better than that of the present Tibet AS array around 20 - 100 TeV.
The Tibet AS+MD array will measure the directions of the celestial TeV
gamma-ray sources and the cutoffs of their energy spectra. Furthermore, the
Tibet AS+MD array, along with imaging atmospheric Cherenkov telescopes as well
as the Fermi Gamma-ray Space Telescope and X-ray satellites such as Suzaku and
MAXI, will make multiwavelength observations and conduct morphological studies
on sources in the quest for evidence of the hadronic nature of the cosmic-ray
acceleration mechanism.Comment: Accepted by Astroparticle Physic
Solar Neutrinos and the Eclipse Effect
The solar neutrino counting rate in a real time detector like
Super--Kamiokanda, SNO, or Borexino is enhanced due to neutrino oscillations in
the Moon during a partial or total solar eclipse. The enhancement is calculated
as a function of the neutrino parameters in the case of three flavor mixing.
This enhancement, if seen, can further help to determine the neutrino
parameters.Comment: 24 Pages Revtex, 8 figures as one ps file. To appear in Phys. Rev. D;
Some typos corrected and a reference adde
Galactic Point Sources of TeV Antineutrinos
High energy cosmic ray experiments have identified an excess from the region
of the Galactic Plane in a limited energy range around eV (EeV). This
is very suggestive of neutrons as candidate primaries, because the directional
signal requires relatively-stable neutral primaries, and time-dilated neutrons
can reach Earth from typical Galactic distances when the neutron energy exceeds
an EeV. We here point out that if the Galactic messengers are neutrons, then
those with energies below an EeV will decay in flight, providing a flux of
cosmic antineutrinos above a TeV which is {\it observable} at a kilometer-scale
neutrino observatory. The expected event rate per year above 1 TeV in a
detector such as IceCube, for example, is 20 antineutrino showers (all flavors)
and a directional signal of 4 events. A measurement of
this flux can serve to identify the first extraterrestrial point source of TeV
antineutrinos.Comment: matches published versio
Constraints on Gamma-ray Emission from the Galactic Plane at 300 TeV
We describe a new search for diffuse ultrahigh energy gamma-ray emission
associated with molecular clouds in the galactic disk. The Chicago Air Shower
Array (CASA), operating in coincidence with the Michigan muon array (MIA), has
recorded over 2.2 x 10^{9} air showers from April 4, 1990 to October 7, 1995.
We search for gamma rays based upon the muon content of air showers arriving
from the direction of the galactic plane. We find no significant evidence for
diffuse gamma-ray emission, and we set an upper limit on the ratio of gamma
rays to normal hadronic cosmic rays at less than 2.4 x 10^{-5} at 310 TeV (90%
confidence limit) from the galactic plane region: (50 degrees < l < 200
degrees); -5 degrees < b < 5 degrees). This limit places a strong constraint on
models for emission from molecular clouds in the galaxy. We rule out
significant spectral hardening in the outer galaxy, and conclude that emission
from the plane at these energies is likely to be dominated by the decay of
neutral pions resulting from cosmic rays interactions with passive target gas
molecules.Comment: Astrophysical Journal, submitted, 11 pages, AASTeX Latex, 3
Postscript figure
A Search for Ultra-High Energy Counterparts to Gamma-Ray Bursts
A small air shower array operating over many years has been used to search
for ultra-high energy (UHE) gamma radiation ( TeV) associated with
gamma-ray bursts (GRBs) detected by the BATSE instrument on the Compton
Gamma-Ray Observatory (CGRO). Upper limits for a one minute interval after each
burst are presented for seven GRBs located with zenith angles . A excess over background was observed between 10 and
20 minutes following the onset of a GRB on 11 May 1991. The confidence level
that this is due to a real effect and not a background fluctuation is 99.8\%.
If this effect is real then cosmological models are excluded for this burst
because of absorption of UHE gamma rays by the intergalactic radiation fields.Comment: 4 pages LaTeX with one postscript figure. This version does not use
kluwer.sty and will allow automatic postscript generatio
Gamma ray astronomy above 30 TeV and the IceCube results
The study of the diffuse Galactic gamma ray emission is of fundamental importance to understand the properties of cosmic ray propagation in the Milky Way, and extending the measurements to E âł 30 TeV is of great interest. In the same energy range the IceCube detector has also recently observed a flux of astrophysical neutrinos, and it is important to test experimentally if the neutrino production is accompanied by a comparable emission of high energy photons. For E âł 30 TeV, the absorption effects due to e+eâ pair production when the high energy photons interact with radiation fields present in space are not negligible and must be taken into account. Gamma rays, in good approximation, are completely absorbed if they have an extragalactic origin, but the absorption is significant also for Galactic photons. In this case the size and angular dependence of the absorption depends on the space distribution of the emission. In this work we estimate the absorption for different models of the space distribution of the gamma ray emission, and discuss the potential of future detectors
A High Statistics Search for Ultra-High Energy Gamma-Ray Emission from Cygnus X-3 and Hercules X-1
We have carried out a high statistics (2 Billion events) search for
ultra-high energy gamma-ray emission from the X-ray binary sources Cygnus X-3
and Hercules X-1. Using data taken with the CASA-MIA detector over a five year
period (1990-1995), we find no evidence for steady emission from either source
at energies above 115 TeV. The derived upper limits on such emission are more
than two orders of magnitude lower than earlier claimed detections. We also
find no evidence for neutral particle or gamma-ray emission from either source
on time scales of one day and 0.5 hr. For Cygnus X-3, there is no evidence for
emission correlated with the 4.8 hr X-ray periodicity or with the occurrence of
large radio flares. Unless one postulates that these sources were very active
earlier and are now dormant, the limits presented here put into question the
earlier results, and highlight the difficulties that possible future
experiments will have in detecting gamma-ray signals at ultra-high energies.Comment: 26 LaTeX pages, 16 PostScript figures, uses psfig.sty to be published
in Physical Review
CASAâMIA: A ââprecisionââ EAS detector
The CASAâMIA detector was constructed to search for sources of UHE neutral radiation. As such it has established limits well below those of previously reported observations and of most contemporaneous detectors. In addition to its primary mission, however, CASAâMIA measures the lateral distribution of both electrons and muons in EAS throughout a range of energies and with a degree of sampling not previously available.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87669/2/207_1.pd
The Composition of Cosmic Rays at the Knee
The observation of a small change in spectral slope, or 'knee' in the fluxes
of cosmic rays near energies 10^15 eV has caused much speculation since its
discovery over 40 years ago. The origin of this feature remains unknown. A
small workshop to review some modern experimental measurements of this region
was held at the Adler Planetarium in Chicago, USA in June 2000. This paper
summarizes the results presented at this workshop and the discussion of their
interpretation in the context of hadronic models of atmospheric airshowers.Comment: 36 pages, 10 figure
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