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CLEOParticle Detectors
Thomas Coan
SMU
• What to detect?
• How to probe?
• What is a “detector?”
• Putting it all together
• Some examples
Thomas Coan/SMU Quarknet 2001
CLEOParticle Properties
• lifetime
• mass
• electric charge• ”spin”
Thomas Coan/SMU Quarknet 2001
CLEOGeneral Idea of Colliding Particle Experiments
• Collide probe particles with target
• Detect particles from collision
• Interpret results
Thomas Coan/SMU Quarknet 2001
CLEOEarly Particle Physics Experiment
Interpretation:
Set-up:
Ernest Rutherford 1909
Thomas Coan/SMU Quarknet 2001
CLEOHow do we “shoot” probe particles?
Acquire some probe particles
Accelerate the probe particles
Steer and aim the probe particles
Final speed c
Thomas Coan/SMU Quarknet 2001
CLEOAccelerator Types
Circular
Thomas Coan/SMU Quarknet 2001
CLEOAccelerator Types
Linear
Thomas Coan/SMU Quarknet 2001
CLEOTarget Types
Colliding beam
Fixed target
Thomas Coan/SMU Quarknet 2001
CLEOWave Nature of Particles
Electron diffraction: particle as wave
Waves interfere:
Thomas Coan/SMU Quarknet 2001
CLEOWhy use higher and higher energies?
= h/p
The more energetic the probe, the finer the accessible detail
Thomas Coan/SMU Quarknet 2001
CLEOCollide
Thomas Coan/SMU Quarknet 2001
CLEOTrajectory measurement
• Charged particle
• Drifting ionized e-
• Electric field
• Noble “fill gas”
“Drift time” DOCA
“curvature” 1/p
Magnetic field curves trajectory
Thomas Coan/SMU Quarknet 2001
CLEOCLEO Drift Chamber
16 axial layers1696 cells
31 stereo layers8100 cells
Thomas Coan/SMU Quarknet 2001
CLEOCLEO Drift Chamber
Thomas Coan/SMU Quarknet 2001
CLEOCLEO Calorimeter
• Measure particle energy (plus position and flight path angle)
• Good for charged and neutral particles
• Particles deposit energy in dense, transparent medium
• Medium produces light, proportional to particle energy
Thomas Coan/SMU Quarknet 2001
CLEOScintillation
• Complicated phenomenon
• Basic idea: convert particle kinetic energy into light
• Amount of light proportional to particle energy
• Light emission is prompt: scintillators useful as timers
• Scintillators used mostly w/ charged particles
Thomas Coan/SMU Quarknet 2001
CLEOSea-level muon detector
PMT
Scintillator
PMT
Scintillator
Photomultiplier tube (PMT)
Photons enter here
Discriminator
Discriminator
Thomas Coan/SMU Quarknet 2001
CLEO
Thomas Coan/SMU Quarknet 2001
CLEODetermine production height of muons
1
2
3
12
3
Earth
Atmosphere
• Sea level flux depends on pathlength from production point
• Changing telescope angle changes pathlength
• Flux change production height h
h
Thomas Coan/SMU Quarknet 2001
CLEOCerenkov Radiation
• Emitted by charged particles only
• Emitted only when particle’s speed in medium exceeds that of light’s
• Pattern of light has cone-like shape:
• Particle’s speed determines shape of cone• Cerenkov detectors measure particle speed Particle momentum (mv) and speed (v) mass
Thomas Coan/SMU Quarknet 2001
CLEOCerenkov Radiation
Cerenkov radiator built here at SMU for CLEO
Thomas Coan/SMU Quarknet 2001
CLEOParticle “Fingerprints”
Thomas Coan/SMU Quarknet 2001
CLEORussian Dolls
Thomas Coan/SMU Quarknet 2001
CLEO“Top” event
Thomas Coan/SMU Quarknet 2001
CLEO
How to “see” neutrinosSudbury Neutrino Observatory (SNO)
Thomas Coan/SMU Quarknet 2001
CLEOCerenkov Light in Action
Thomas Coan/SMU Quarknet 2001
CLEOSudbury Neutrino Observatory
Thomas Coan/SMU Quarknet 2001
CLEOSummary
Variety of detector types
Detector combinations are the key
Detector behavior is understandable
