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

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Two techniques:

• detect shower particles on the ground

• detect air fluorescence produced by shower particles

Beyond 1500 gm/cm2

electromagnetic particlesabsorbed. (Highly inclined showers)

90 % of particleswithin Moliereradius of ≤ 100 m

Thin scintillators measure principally electrons andpositrons.

A deep water detector measures roughly the total energy flux of the shower particles at its location.

Note: total energy inentire showercarried by muons ≤ 10%

Energy deposit in1.2 meters of water

At 1000 meters from core

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Signal processing can extract em/muon ratio

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Old Shower: pure muons

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

Mono 26.15 ± 0.55 km

Hybrid 25.96 ± 0.02 kmCalibration with central laser facility and Celeste

Chii vs time

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16th

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S1000 isEnergy parameter