Particle Detectorslibvolume7.xyz/.../particledetectors/particledetectorspresentation1.pdf · CLEO...
Transcript of Particle Detectorslibvolume7.xyz/.../particledetectors/particledetectorspresentation1.pdf · CLEO...
CLEOParticle Detectors
Thomas Coan
SMU
•What to detect?
•How to probe?
•What is a “detector?”
• Putting it all together
• Some examples
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Thomas Coan/SMU Quarknet 2001
Particle Properties
• lifetime
•mass
• electric charge
• ”spin”
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General Idea of Colliding Particle Experiments
• Collide probe particles with target
• Detect particles from collision
• Interpret results
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Early Particle Physics Experiment
Interpretation:
Set-up:
Ernest Rutherford 1909
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How do we “shoot” probe particles?
�Acquire some probe particles
�Accelerate the probe particles
� Steer and aim the probe particles
Final speed ∼ c
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Accelerator Types
Circular
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Accelerator Types
Linear
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Target Types
Colliding beam
Fixed target
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Wave Nature of Particles
Electrondiffraction: particle as wave
Waves interfere:
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Why use higher and higher energies?
λλλλ = h/p
∴∴∴∴The more energetic the probe, the finer the accessible detail
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Collide
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Trajectory measurement
•Charged particle
•Drifting ionized e-
•Electric field
•Noble “fill gas”
∴“Drift time” ⇒ DOCA
“curvature” ∝ 1/p
Magnetic field curves trajectory
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CLEO Drift Chamber
16 axial layers
1696 cells
31 stereo layers
8100 cells
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CLEO Drift Chamber
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CLEO 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
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Scintillation
•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
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Sea-level muon detector
PMT
Scintillator
PMT
Scintillator
Photomultiplier tube (PMT)
Photons enter here
µ
Discriminator
Discriminator
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Determine production height of muons
1
2
3
12
3
Earth
Atmosphere
• Sea level µµµµ flux depends on pathlength from production point
•Changing telescope angle changes pathlength
• Flux change ⇒⇒⇒⇒ production height ∆∆∆∆h
∆∆∆∆h
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Cerenkov 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
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Cerenkov Radiation
Cerenkov radiator built here at SMU for CLEO
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Particle “Fingerprints”
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Russian Dolls
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“Top” event
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How to “see” neutrinos
Sudbury Neutrino Observatory (SNO)
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Cerenkov Light in Action
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SudburyNeutrino Observatory
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Summary
Variety of detector types
Detector combinations are the key
Detector behavior is understandable