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Detection ot the Highest Energy Cosmic Rays Lecture 1 The Violent Universe Nucl Phys B (Proc Suppl) 138 (2005) 465-491 Taup Conference Proceedings 2004 James W. Cronin Les Houches, March 19,2007. Assume E -2.5 spectrum. 4. 5.
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Detection ot the Highest Energy Cosmic Rays Lecture 1 The Violent Universe Nucl Phys B (Proc Suppl) 138 (2005) 465-491 Taup Conference Proceedings 2004 James W. Cronin Les Houches, March 19,2007
Two techniques: • detect shower particles on the ground • detect air fluorescence produced by shower particles
Beyond 1500 gm/cm2 electromagnetic particles absorbed. (Highly inclined showers)
90 % of particles within Moliere radius of ≤ 100 m
Thin scintillators measure principally electrons and positrons. A deep water detector measures roughly the total energy flux of the shower particles at its location.
Note: total energy in entire shower carried by muons ≤ 10%
Energy deposit in 1.2 meters of water
9 Signal processing can extract em/muon ratio
pe /A = (/4)(/rp)Ne pe/A = photoelectrons/meter2 • = photocathode efficiency x mirror reflectivity ~ 0.16 • = fluorescence yield ~ 4.5 UV photons/meter/particle = 1 degree = 0.0175 rp = perpendicular distance to shower axis ~ 20 km • = attenuation ~ exp(rp/) ~ exp(-20/10) ~ 0.135 Ne = number of charged shower particles ~ 7x109 for 1019 EeV pe/A ~ 50 photoelectrons/meter2/degree
Chii vs time Mono 26.15 ± 0.55 km Hybrid 25.96 ± 0.02 km Calibration with central laser facility and Celeste
S1000 is Energy parameter 8