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Particle Detection and Identification Masterclass in Manchester

Join the Particle Physics Masterclass in Manchester to learn about detecting and identifying particles. Explore various methods, from scintillation to tracking detectors, to spot particles like electrons, muons, and hadrons. Gain insights on tracking paths of charged particles and using calorimeters to measure energy. Discover detectors like DELPHI, BaBar, and ATLAS, and delve into the complexities of identifying particles, including muons and hadrons. Learn about quarks, gluons, and elementary particle detection techniques. Enhance your understanding of particle physics with the latest advancements in detection technology.

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Particle Detection and Identification Masterclass in Manchester

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  1. Particle Detection and Identification Roger Barlow Particle Physics Masterclass Manchester, March 20th 2008

  2. Studying Particles • Detection: Where are they? Very small Too small to see • Identification: What are they? The particle-spotters’ guide

  3. Detecting particles Rule 1: You can’t detect neutral particles, only charged particles. Rule 2: You can only detect charged particles if they’re moving – quite fast. Rule 3: Even then the signals are small and need amplifying Rule 4: You can only detect charged particles with ‘long’ lifetimes, i.e. >~1 ns. That basically means e, , , K, p

  4. Small but with a big kick Charged Particle Excited electron Electric Field What next? Two options ATOM

  5. Option 1: Excited to a higher level Photon Drops back

  6. Many atoms – many photons Scintillation particle Light • Good for measuring • Timing • Energy loss • Bad for measuring • position Collected and amplified by photomultiplier

  7. Option 2: Excited all the way out Positive ion Free electron

  8. Tracking detectors Electrons=charge=current Wire in a gas Big field near wire Amplification through avalanche process Good for position Wire At ~1 kV Geiger counter Multiwire chambers Drift chambers

  9. Tracking Chambers + - - + - + - + - + - + - + + - - + - +

  10. Summary so far We can detect a fast charged particle in all sorts of ways, based on • Scintillation • Ionisation What next?

  11. Birds: Size Shape Colour Sound Behaviour Particles Size Shape Colour Sound Behaviour Identification: What are they? electron Hadron (pi, K) muon proton positron

  12. What Charge is it? + or - ? Apply a magnetic field Particle curves to right or left depending on its charge Bonus: faster particles curve less Bend depends on momentum This measures momentum and direction

  13. Tracking B Path of a charged particle A measured point

  14. Spotting electrons/positrons Intersperse • Sensitive material – scintillators or tracking chambers • Dense material – sheets of iron or lead (or …) Electrons and positrons shower rapidly e- e-   e+ e- Hadrons shower more slowly Collide with protons/neutrons and produce more hadrons Muons don’t shower No strong interaction Bonus: photons convert to electrons and then shower Bonus: size of shower gives the energy

  15. Calorimeters Electron-positron Pair Incoming electron, positron or photon Shower of secondary particles • Count number of secondary particles in showerenergy of incoming particle

  16. Spotting muons Do not interact much • No shower in calorimeter • Penetrate through shielding Muon detector = charged particle detector put where other charged particles would be screened out Muon in Muon out Absorber

  17. Spotting hadrons Anything that is not a muon or an electron is a hadron (pion, kaon, proton) Telling the difference is possible but more complicated and less reliable…

  18. Parts of a Detector Muon chambers B Tracking Calorimeters

  19. DELPHI Detector

  20. Another detector: BaBar

  21. Yet another detector: ATLAS

  22. What about quarks? u,d,s,c,b,t • Never been seen directly • Manifest as jets of hadrons Bonus: gluons look almost just like quarks

  23. Quarks are jets e+ e- q q Many tracks Mostly hadrons Hadrons collimated into jets Jets back to backs

  24. Conclusion Elementary particles are very small BUT we can detect them Lots of different techniques – no single best method New ideas evolving all the time Yesterday’s detectors look primitive compared to today’s sophisticated and ingenious devices Tomorrow’s will be even better.

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