1,441 research outputs found
Observations with the HEGRA stereoscopic system
The HEGRA system of imaging air Cherenkov telescopes has successfully
pioneered the stereoscopic observation technique of extensive air showers. The
observational method is briefly described and important results of recent
observations of sources of photons with TeV( eV)-energies are
summarized: The first detection of a TeV -ray signal from the
shell-type supernova remnant Cassiopeia A and preliminary results obtained from
the observation of strong variability of the extragalactic source Mkn 421
during observations carried out from February to May 2000.Comment: 4 pages, 3 figures, to appear in the Proceedings of the XXIst
Rencontres de Moriond "Very High Energy Phenomena in the Universe", Les Arcs,
France, Jan. 20-27 (2001
Pair-production opacity at high and very-high gamma-ray energies
The propagation of high energy (HE, MeV) and very high-energy
gamma-rays (VHE, GeV) in the extra-galactic photon field leads
to pair-production and consequently energy- and distance-dependent attenuation
of the primary intensity. The spectroscopy of an increasing number of
extra-galactic objects at HE and VHE energies has demonstrated indeed the
presence of such an attenuation which in turn has been used to constrain the
photon density in the medium. At large optical depth ()
potential modifications of pair-production due to competing but rare processes
(as, e.g., the presence of sub-neV axion-like particle) may be found.
Indications for a pair-production anomaly have previously been found with
VHE-spectra. Here, we present further indications (at the level of ) for a reduced optical depth at high energies from an analysis of
Fermi-\textit{LAT} data.Comment: 4 pages, 2 figures, to be published in the proceedings
(DESY-PROC-2013-04) of the 9th patras worksho
Occupational profiles and training requirements at Level 3 in the Spanish textile and clothing industry
AstroFit: An Interface Program for Exploring Complementarity in Dark Matter Research
AstroFit is an interface adding astrophysical components to programs for
fitting physics beyond the Standard Model (BSM) to experimental data from
collider searches. The project aims at combining a wide range of experimental
results from indirect, direct and collider serarches for Dark Matter (DM) and
confronting it with theoretical expectations in various DM models. Here, we
introduce AstroFit and discuss first results.Comment: 6 pages, 3 figures, proceedings for the 13th ICATPP Conference on
Astroparticle, Particle, Space Physics and Detectors for Physics
Applications, Villa Olm
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