1,239 research outputs found
Primary Particle Type of the Most Energetic Fly's Eye Air Shower
The longitudinal profile of the most energetic cosmic-ray air shower measured
so far, the event recorded by the Fly's Eye detector with a reconstructed
primary energy of about 320 EeV, is compared to simulated shower profiles. The
calculations are performed with the CORSIKA code and include primary photons
and different hadron primaries. For primary photons, preshower formation in the
geomagnetic field is additionally treated in detail. For primary hadrons, the
hadronic interaction models QGSJET01 and SIBYLL2.1 have been employed. The
predicted longitudinal profiles are compared to the observation. A method for
testing the hypothesis of a specific primary particle type against the measured
profile is described which naturally takes shower fluctuations into account.
The Fly's Eye event is compatible with any assumption of a hadron primary
between proton and iron nuclei in both interaction models, although differences
between QGSJET01 and SIBYLL2.1 in the predicted profiles of lighter nuclei
exist. The primary photon profiles differ from the data on a level of ~1.5
sigma. Although not favoured by the observation, the primary photon hypothesis
can not be rejected for this particular event.Comment: 20 pages, 8 figures; v2 matches version accepted by Astroparticle
Physic
Characteristics of geomagnetic cascading of ultra-high energy photons at the southern and northern sites of the Pierre Auger Observatory
Cosmic-ray photons above 10^19 eV can convert in the geomagnetic field and
initiate a preshower, i.e. a particle cascade before entering the atmosphere.
We compare the preshower characteristics at the southern and northern sites of
the Pierre Auger Observatory. In addition to a shift of the preshower patterns
on the sky due to the different pointing of the local magnetic field vectors,
the fact that the northern Auger site is closer to the geomagnetic pole results
in a different energy dependence of the preshower effect: photon conversion can
start at smaller energies, but large conversion probabilitites (>90%) are
reached for the whole sky at higher energies compared to the southern Auger
site. We show how the complementary preshower features at the two sites can be
used to search for ultra-high energy photons among cosmic rays. In particular,
the different preshower characteristics at the northern Auger site may provide
an elegant and unambiguous confirmation if a photon signal is detected at the
southern site.Comment: 25 pages, 14 figures, minor changes, conclusions unchanged, Appendix
A replaced, accepted by Astroparticle Physic
B779: Ectomycorrhizae of Maine. 2 A Listing of Lactarius with the Associated Hosts (with Additional Information on Edibility)
Thirty-nine Lactarii have been collected and identified with their possible ectomycorrhizal associates for Maine. Many of the Lactarius are new reports for Maine. Most of the ectomycorrhizal relationships reported from Maine are confirmed by the work of others. The edibility comments are those of the authors from the popular mushroom guides mentioned. Colored photos of thirty-nine Lactarii are included.https://digitalcommons.library.umaine.edu/aes_bulletin/1012/thumbnail.jp
Search for photons at the Pierre Auger Observatory
The Pierre Auger Observatory has a unique potential to search for ultra-high
energy photons (above ~1 EeV). First experimental limits on photons were
obtained during construction of the southern part of the Observatory.
Remarkably, already these limits have proven useful to falsify proposals about
the origin of cosmic rays, and to perform fundamental physics by constraining
Lorentz violation. A final discovery of photons at the upper end of the
electromagnetic spectrum is likely to impact various branches of physics and
astronomy.Comment: 5 pages, 5 figures. Presented at CRIS 2008, Malfa, Ital
On a possible photon origin of the most-energetic AGASA events
In this work the ultra high energy cosmic ray events recorded by the AGASA
experiment are analysed. With detailed simulations of the extensive air showers
initiated by photons, the probabilities are determined of the photonic origin
of the 6 AGASA events for which the muon densities were measured and the
reconstructed energies exceeded 10^20 eV. On this basis a new, preliminary
upper limit on the photon fraction in cosmic rays above 10^20 eV is derived and
compared to the predictions of exemplary top-down cosmic-ray origin models.Comment: 3 pages, 1 figure, 2 tables; presented at XIII ISVHECRI, Pylos,
Greec
B810: Ectomycorrhizae of Maine 3. A Listing of Hygrophorus with Associated Hosts
Hygrophori have been collected and identified with their possible ectomycorrhizal associates in Maine. Most of the ectomycorrhizal relationships reported from Maine were confirmed by the work of others. The information on edibility is from authors\u27 popular mushroom guides. Colored photos of forty-four Hygrophori are included here.https://digitalcommons.library.umaine.edu/aes_bulletin/1011/thumbnail.jp
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Novel concept of multi-channel fiber optic surface plasmon resonance sensor
A novel multi-channel fiber optic surface plasmon resonance (SPR) sensor is reported. The sensing structure consists of a single-mode optical fiber, covered with a thin gold layer, which supports a surface plasmon (SP), and a Bragg grating. The Bragg grating induces coupling between the forward-propagating fundamental core mode and the back-propagating SP-cladding mode. As the SP-cladding modes are highly sensitive to changes in the refractive index of the surrounding medium, the changes can be accurately measured by spectroscopy of these hybrid modes. Multichannel capability is achieved by employing a sequence of Bragg gratings of different periods and their reading via the wavelength division multiplexing. Theoretical analysis and optimization based on the coupled-mode theory (CMT) is carried out and performance characteristics of the sensor are determined
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