The Knee: Theory and Experiment Yodh, Gaurang B
Journal of physics. Conference series,
10/2006, Volume:
47, Issue:
1
Journal Article
Peer reviewed
Open access
A review of current status of theoretical paradigm and results of direct and indirect experiments to study cosmic rays through the knee region are presented and discussed. There is general agreement ...that the knee is around a PeV and that it reflects a rigidity cutoff. The composition of cosmic rays in the knee region is mixed and changing with energy. The two direct experiments, JACEE and RUNJOB with measurements in the 100 TeV per particle to 1000 TeV per particle and with similar exposures do not agree. While JACEE indicates a increase in ⟨lnA⟩ from its low energy value of 1.5 to a value closer to 3 , the RUNJOB experiment sees no change in the composition albeit with large uncertainty. Of the indirect experiments, KASKADE, SPASEAMANDA, HEGRA-Airobic, CACTI, TUNKA and Tibet favor Heavy composition above the knee and beyond. The KASKADE energy range extends to 100 PeV where their analysis indicates iron dominance. KASKADE does not see a proton rigidity cutoff until about 3 PeV, while Tibet measures a steepening of the proton slope at a few hundred TeV. BLANCA and DICE favor little composition change or a change towards a proton dominated composition around 10 PeV. We need experiments with much better mass resolution in the energy range of the knee and a more quantitative understanding of the hadron production in the forward region at these energies to make definitive progress.
This paper discusses the properties of using the water Cherenkov technique to detect air showers in the few hundred GeV to 100 TeV energy range. The responses of a 6 sq m 2 m deep water Cherenkov ...counter and of a 6 sq m 10 cm thick scintillator-lead sandwich counter to air shower electrons and photons are described. The advantages of the water Cherenkov detector are outlined. Its application to VHE gamma ray astronomy is discussed with particular reference to the MILAGRO telescope currently under construction. MILAGRO, a water-Cherenkov detector for gamma ray astronomy above 100 Gev, uses an existing pool of 60 x 80 x 8 m, located in the Jemez mountains near Los Alamos, NM. The threshold of the MILAGRO detector is comparable to atmospheric Cherenkov detectors; however, it has several advantages over these optical detectors. MILAGRO can operate 24 hours a day in all weather conditions and it has an open aperture which allows it to view the entire northern sky every day. These capabilities allow for a systematic all-sky survey to be done for the first time at these energies. (Author)
This paper presents a summary of the results the CACTI experiment, which studied the shape of Cherenkov lateral distributions of showers triggering the CYGNUS II air shower array at Los Alamos ...National Laboratory, to investigate the composition of cosmic rays in the PeV energy range.
The MILAGRO gamma ray observatory Yodh, Gaurang B.
Nuclear physics. Section B, Proceedings supplement,
1997, Volume:
52, Issue:
3
Journal Article
Open access
MILAGRO will be the first water-Cherenkov detector specifically built to study extensive air showers. It is being built in an existing man-made pond 60 m
times 80 m by 8 m, located in the Jemez ...mountains near Los Alamos, NM. Unlike conventional air shower detectors, which sample less than 1% of the particles which reach detector level, MILAGRO will be totally sensitive to electrons, photons, hadrons, and muons hitting the detector. The threshold of the MILAGRO detector is comparable to atmospheric Cherenkov detectors, however it has several advantages over these optical detectors. MILAGRO is operational 24 hours a day in all weather conditions and it has an open aperture which allows it to view the entire northern sky every day. These capabilities allow for a systematic all-sky survey to be done for the first time at these energies. MILAGRO will search for point sources of VHE gamma radiation, both steady and episodic. MILAGRO will measure the Crab spectrum with high significance and possibly locate a cut off in the spectrum. In addition, it will detect and measure the spectra from AGN's such as MRK 421. MILAGRO will be the first VHE detector capable of recording Gamma Ray Bursts at energies above 250 GeV. The physics merits of this detector together with its design and current status are discussed.
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