1. Particle Detectors ThomasCoan SMU • What to detect? • How to probe? • What is a “detector?” • Putting it all together • Some examples

2. Quarknet 2001 ParticleProperties • mass • lifetime • electric charge • ”spin”

3. Quarknet 2001 GeneralIdeaofCollidingParticleExperiments • Collide probe particles with target • Detect particles from collision • Interpret results

4. Quarknet 2001 EarlyParticlePhysicsExperiment ErnestRutherford1909 Set-up: Interpretation:

5. Quarknet 2001 How do we “shoot” probe particles? • Acquire some probe particles • Accelerate the probe particles Final speed  c • Steer and aim the probe particles

6. Quarknet 2001 AcceleratorTypes Circular

7. Quarknet 2001 AcceleratorTypes Linear

8. Quarknet 2001 TargetTypes Collidingbeam Fixed target

9. Quarknet 2001 Wave Nature of Particles Wavesinterfere: Electrondiffraction: particle as wave

10. Quarknet 2001 Why use higher and higher energies?  = h/p The more energetic the probe, the finer the accessible detail

11. Quarknet 2001 Collide

12. Quarknet 2001 Trajectory measurement • Chargedparticle • Noble “fill gas” • Electric field • Driftingionized e- “Drifttime”  DOCA Magneticfieldcurvestrajectory “curvature”  1/p

13. Quarknet 2001 CLEO Drift Chamber

14. Quarknet 2001 CLEO Drift Chamber

15. Quarknet 2001 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. Quarknet 2001 Scintillation • Complicatedphenomenon • 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. Quarknet 2001 PMT Scintillator Sea-levelmuondetector  Discriminator Discriminator PMT Scintillator Photons enter here Photomultiplier tube (PMT)

18. Quarknet 2001

19. Quarknet 2001 Determineproductionheightofmuons 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. Quarknet 2001 CerenkovRadiation • 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

21. Quarknet 2001 CerenkovRadiation CerenkovradiatorbuilthereatSMU for CLEO

22. Quarknet 2001 Particle “Fingerprints”

23. Quarknet 2001 RussianDolls

24. Quarknet 2001 “Top” event

25. Quarknet 2001 How to “see” neutrinosSudbury Neutrino Observatory (SNO)

26. Quarknet 2001 Cerenkov Light in Action

27. Quarknet 2001 SudburyNeutrinoObservatory

28. Quarknet 2001 Summary Variety of detector types Detector combinations are the key Detector behavior is understandable