Particle Detectors

1
Particle Detectors
Thomas Coan SMU

• What to detect?
• How to probe?
• What is a detector?
• Putting it all together
• Some examples

2
Particle Properties

• mass

• lifetime

• electric charge

• spin

3
General Idea of Colliding Particle Experiments

• Collide probe particles with target
• Detect particles from collision
• Interpret results

4
Early Particle Physics Experiment
Ernest Rutherford 1909
Set-up
Interpretation
5
How do we shoot probe particles?

• Acquire some probe particles

• Accelerate the probe particles

Final speed ? c

• Steer and aim the probe particles

6
Accelerator Types
Circular
7
Accelerator Types
Linear
8
Target Types
Colliding beam
Fixed target
9
Wave Nature of Particles
Waves interfere
Electron diffraction particle as wave
10
Why use higher and higher energies?
? h/p
?The more energetic the probe, the finer the
accessible detail
11
Collide
12
Trajectory measurement

• Charged particle

• Noble fill gas

• Electric field

• Drifting ionized e-

?Drift time ? DOCA
Magnetic field curves trajectory
curvature ? 1/p
13
CLEO Drift Chamber
14
CLEO Drift Chamber
15
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

16
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

17
Sea-level muon detector
?
Discriminator
Discriminator
PMT
Scintillator
Photons enter here
Photomultiplier tube (PMT)
18
(No Transcript)
19
Determine production height of muons
2
1
Atmosphere
3
1
2
3
?h
Earth

• Sea level ? flux depends on pathlength from
  production point

• Changing telescope angle changes pathlength

• Flux change ? production height ?h

20
Cerenkov Radiation

• Emitted by charged particles only

• Emitted only when particles speed in medium
  exceeds that of lights

• Pattern of light has cone-like shape

• Particles speed determines shape of cone

• Cerenkov detectors measure particle speed

• Particle momentum (mv) and speed (v) ? mass

21
Cerenkov Radiation
Cerenkov radiator built here at SMU for CLEO
22
Particle Fingerprints
23
Russian Dolls
(Anna Kournakova?)
24
Top event
25
How to see neutrinosSudbury Neutrino
Observatory (SNO)
26
Cerenkov Light in Action
27
Sudbury Neutrino Observatory
28
Summary
Variety of detector types
Detector combinations are the key
Detector behavior is understandable