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Particle Detectors (7)

Particle Detectors (7). Robert W. Lambert, NIKHEF, FOM, VU Amsterdam, NL. cern.ch/ rlambert /lectures. rob.lambert@cern.ch. Welcome Back!. Memory test?. Summary of my last lecture?. Summary of last lecture. Abuse the power of dynamic electromagnetism in a medium …. g < 10.

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Particle Detectors (7)

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  1. Particle Detectors (7) Robert W. Lambert, NIKHEF, FOM, VU Amsterdam, NL cern.ch/rlambert/lectures rob.lambert@cern.ch Nikhef, April/May 2013

  2. Welcome Back! Nikhef, April/May 2013

  3. Memory test? • Summary of my last lecture? Nikhef, April/May 2013

  4. Summary of last lecture Abuse the power of dynamic electromagnetism in a medium … g < 10 10 < g < 100 g > 1000 ns, accuracy required, alas poor OPERA miscalibration :S Nikhef, April/May 2013

  5. Tracking Particles don’t travel in straight lines! Resolution varies detector-to-detector,hit-to-hit Thee stages of tracking: Seeding (Simple pattern recognition) Finding (Hough transform or Kalman filter) Fitting (Chi2 minimization) Ghost rate vs. efficiency! No tracker can do everything Nikhef, April/May 2013

  6. Hitting things Nikhef, 1st March 2013

  7. Lecture series • 2rd April: Detectors, History & Principles • 5th April: Detecting Light • 8th April: Cherenkov & Transition radiation 4-6. Olya: Tracking: Gas, Semiconductors, Fitting • 23rd April: Calorimetry & Advice on presentations • 26th April: Student Presentations (Oral Exam) • 3rd May: Radiation Hardness & Weakly interacting particles • 7th May: Putting it all together & Building an experiment 11-14. Olya:Accelerators, Atlas vs CMS,Medical, R&D Visit Nikhef, April/May 2013

  8. Rob: Oral Presentation • Date: 26th April (Friday!) • Aims: • To demonstrate you know about detectors, live, in person • To collaborate on an experimental topic • To unlearn all the bad habits of particle physics presentations • To prepare you in justifying technologies in front of your peers • Topic: Your choice • A subdetector technology battle: Why choose A instead of B? • An interesting and crazy experiment: what cool technologies are out there? • Format: 15 min presentation, teams of two, in front of the class/guests • You will be marked on: • Presentation skills • Topical Understanding • Technical Detail I’m prepared to be impressed! Sign up sheets start Today … Discuss with me during the break Or: Email me after the lecture Nikhef, April/May 2013

  9. Today Getting Hot Staying Cool HEP Calorimetry Advice on Presentations Nikhef, April/May 2013

  10. Apologies Nikhef, April/May 2013

  11. Part 1 Calorimetry Nikhef, April/May 2013

  12. Outline of part 1 • Hadronic or Electromagnetic? • Homogeneous or Sampling? • Compensating? Calorimetry Resolutions E/ E = a /  E  b/ E  c real-world examples Why?? Particle Flow Nikhef, April/May 2013

  13. Calorimeters • “Calorimetry:is the science of measuring the heat of chemical reactions or physical changes.” • Calorimetry:is derived from the Latin word calor, meaning heat • Do we ever do calorimetry? Nikhef, April/May 2013

  14. Real Calorimeters • ATLAS mark II ? Nikhef, April/May 2013

  15. Thompson • “Calorimetry: is the science of measuring the heat of chemical reactions or physical changes.” • Almost! “He estimated the mass of cathode rays by measuring the heat generated when the rays hit a thermal junction and comparing this with the magnetic deflection of the rays.” .. First particle physics calorimeter?? Nikhef, April/May 2013

  16. Bubble Chamber • “Calorimetry: is the science of measuring the heat of chemical reactions or physical changes.” • Almost! Nikhef, April/May 2013

  17. So… we don’t do calorimetry … What do we do??? Nikhef, April/May 2013

  18. So… Transduce: “To convert (energy) from one form to another.” we don’t do calorimetry … (the girl from tomorrow,1990 Australia) Nikhef, April/May 2013

  19. So… Transduce: “To convert (energy) from one form to another.” we don’t do calorimetry … (the girl from tomorrow,1990 Australia) Temperature: A measure of the thermal energy per particle of matter or radiation. Measured by a thermometer Yes, that’s right… … we build really big thermometers! Nikhef, April/May 2013

  20. Guinness Records? • World’s tallestthermometer … • 40.8 metres tall • 34.8 metric tonnes Are you impressed? Nikhef, April/May 2013

  21. KATRIN • I think we beat that one … Nikhef, April/May 2013

  22. KATRIN • Ah, OK, I cheated … it’s actually a spectrometer … • But the experiment is one big thermometer for electrons Nikhef, April/May 2013

  23. KATRIN • Smart choice of manufacturer … Nikhef, April/May 2013

  24. KATRIN • 9000 km round-trip …. Nikhef, April/May 2013

  25. Particle Physics Calo • A thermometer for particle and/or jet energies • Transducer for kinetic energy to light or electrical signals Nikhef, April/May 2013

  26. Particle Physics Calo Nikhef, April/May 2013

  27. Particle Physics Calo Nikhef, April/May 2013

  28. Showers • Two very different types of showers, from EM or Hadrons Electrons heavilyboosted, so multiple scatteringdominates Moliere Radius <pT> ~ 0.35 GeVc-1 Nikhef, April/May 2013

  29. Shower development • Electromagnetic • Hadronic High Energy Low Energy High Energy Low Energy Nikhef, April/May 2013

  30. Shower development • Electromagnetic • Hadronic High Energy Low Energy Full absorption within a few cm High Energy Low Energy Resonance spectrumand lifetime dependson species and material t(p0) = 8.4×10−17s ~ a few nm -> mm Total cross-section depends on species and material Nikhef, April/May 2013

  31. Shower development • Electromagnetic • Hadronic Shapes are very different Nikhef, April/May 2013

  32. Shower development • Electromagnetic • Hadronic Position of first interaction is very different Nikhef, April/May 2013

  33. Shower development • Electromagnetic • Hadronic Containment is very different “punch through” Can develop asymmetrically Nikhef, April/May 2013

  34. Material Properties • Absorbers will be high density, but li and X0 are very different Nikhef, April/May 2013

  35. Some are extreme These materials happen to be …Scintillators! Separate EM showers from hadronic showers So, we identify two basic design concepts: One calorimeter for everything, very good tracker and other PID systems Separate an EM and Hadroniccalo Nikhef, April/May 2013

  36. EM showers Stops when somecritical energy isreached … Nikhef, April/May 2013

  37. Critical Energy • The energy at which an electron loses as much energy in collisions as in radiation OK, almost right ?? This is where showering “stops” Nikhef, April/May 2013

  38. Critical Length Showers can be containedwithin ~20 radiation lengths, fluctuations occur fromposition of first radiation! Nikhef, April/May 2013

  39. Characteristic Width • RM: radius of a cylinder containing 90% of the shower Critical energy, where interaction cross-sectionand brehmstrahlung are approximately equal … Nikhef, April/May 2013

  40. Characteristic Depth • Not 50% of the energy will be lost to that first bremsstrahlung Ec ~ few MeVc-2 Nikhef, April/May 2013

  41. Characteristic Multiplicity • There will be a different number of e compared to g Nikhef, April/May 2013

  42. Characteristic Shape • The shower development is like an exponential decay Nikhef, April/May 2013

  43. Characteristic Maximum • Peak number of particles at a given depth (after this a simpleexponential decay …) Nikhef, April/May 2013

  44. It’s complicated … Nikhef, April/May 2013

  45. To sample? • Homogeneous, absorb all energy in active material • Sampling, sandwich of short X0 and long X0 layers (or li) L = n X0a <X0> = X0b L L = m X0a +p X0b <X0> = (m X0a +p X0b)/(p+m) L Nikhef, April/May 2013

  46. Homogeneous Calo • Homogeneous ECal are likely to be < 1m long @ ~100 GeV • Homogeneous HCal are likely to be > 10m long @ ~ 100 GeV • Since you absorb all the energy, the dominant errors are Poissonian … • There will be other terms … Nikhef, April/May 2013

  47. Sampling Calo • Sampling calorimeters can be simpler and cheaper Heavy insensitive absorber, Lead … Uranium! or Gold?! A few cm of activescintillator material • Sampling calorimeters can be simpler and cheaper • Important for hadronic calorimeters! Nikhef, April/May 2013

  48. Sampling Calo • The ATLAS calorimeters Atlas Tile Cal Atlas Liquid Argon Nikhef, April/May 2013

  49. Historical Calo Nikhef, April/May 2013

  50. Historical Calo Nikhef, April/May 2013

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