Elementary Particle Physics Part 2 Detectors Manfred Jeitler WS 2007/2008

1. Elementary Particle PhysicsPart 2DetectorsManfred JeitlerWS 2007/2008

2. various types of interactionof particles and matter • ionisation • inelastic scattering on electrons • elastic scattering on nuclei • nuclear reactions • Cherenkov radiation • bremsstrahlung • practically only for electrons and positrons • for photons: • photoelectric effect • Compton scattering • pair formation

3. types of detectors • 1. photographic emulsions • 2. scintillators • 3. ionisation detectors • 3.1 gas detectors • 3.2 ionisation in liquids • 3.3 semiconductor detectors • 4. cloud and bubble chambers • 5. Cherenkov and transition radiation detectors

5. the Bethe-Bloch equation

6. scintillators: • simple • fast • still used today scintillator light guides

7. particle entrance window high voltage RHV >> RA amplifier ground Geiger-Müller counter

8. positron in cloud chamber

9. bubble chamber: • one of the main types of detector between 1960 and 1975 • vessel with superheated liquid • beam particles react with molecules in liquid • ionization yields “seeds” where bubbles form • visible tracks are photographed

11. decay of a “charmed” baryon (Σc++)

13. multiwire proportional chamber

14. drift chamber

15. KLOE drift chamber

16. time projection chamber

17. heavy-ion collisions at RHIC: the STAR TPC

18. the NA48 liquid-krypton calorimeter • measures decays of kaons into neutral particles: K0p0p04g • filled with 9 m3 of liquid krypton • part of trigger electronics built by HEPHY, Vienna

19. the liquid-krypton calorimeter of the NA48 experiment (CERN) (electrode structure)

20. + Vbias semiconductor detectors

22. “barrel” of the CMS tracker

23. Cherenkov radiation in a pool-type reactor

24. principle of the Cherenkov effect

25. Experiment NA48 at CERN (measurement of CP-violation): example of a fixed-target experiment

26. muon ring anti hadron calorimeter ring anti DCH DCH magnet DCH DCH The detector of the NA48 experiment at CERN • muon detector and anti-counters for background suppression • electromagnetic liquid-krypton calorimeter for measuring p0p0-decays • hodoscope for exact timing • spectrometer (consisting of 4 drift chambers and a magnet) and hadron calorimeter for measuring p+p--decays

27. Fixed-Target experiment NA48 at CERN: products of one decay in the various parts of the detector

28. CMS

29. rapidity and pseudorapidity • rapidity r : • for a particle moving along the beam axis • rapidity is additive • differently from velocity • same number of events are expected for rapidity intervals of same size • pseudorapidity η • depends only on angle θ with beam axis • easier to calculate • η ~ r for relativistic particles

30. the tracker the task: reconstructing particles and their movement in the detector Tracks of particles in a typical collider experiment of the future (CMS @ LHC)

31. CMS muon detector endcap calorimeter endcap

32. superconducting solenoid Cherenkov detector calorimeter time-of-flight detector tracking chamber vertex detector muon chambers 3.5 GeV e+ 8 GeV e -

34. what happens to the detectors’ data? • detecting the particles is only half the story • they have to be read out • today, too fast to “take notes by hand” • must be converted automatically to digital data • ADC = Analog-to-Digital Converter • TDC = Time-to-Digital Converter • Flash-ADC (histogram over time) • not all information can be read out (readout bandwidth, cost of storage) --> have to “trigger”