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Experimental techniques of High Energy and Nuclear Physics • Introduction to detectors discuss a few typical experiments • Probability, statistics, and data analysis (Leo, ch 4) distributions, maximum likelihood, least squares fitting, lying • Passage of radiation through matter (Leo, ch 2) light and heavy charged particles and photons • Scintillation devices (Leo, ch 7, 8, 9) counters and calorimeters, energy measurement • Ionization devices (Leo, ch 6) proportional and drift chambers, momentum measurement • Semiconductor devices (Leo, ch 10) silicon microstrip detectors, vertexing 880.A20 Winter 2002 Richard Kass References • • • • • • • • • • • Techniques for Nuclear and Particle Physics Experiments, Leo Particle Detectors, Grupen The Physics of Particle Detectors, Green Detectors for Particle Radiation, Kleinknecht The Particle Detector BriefBook, Bock and Vasilescu http://www.cern.ch/Physics/ParticleDetector/BriefBook Particle Data Book (FREE! ORDER ONE TODAY) http://pdg.lbl.gov Introduction to Experimental Particle Physics, Fernow Statistics for Nuclear and Particle Physicists, Lyons Probability and Statistics in Particle Physics, Frodesen, Skjeggestad, Tofe Statistical Data Analysis, Cowen Statistics, Barlow 880.A20 Winter 2002 Richard Kass Intro to HEP Experiments What are the ingredients of a high energy or nuclear physics experiment? Consider three examples of different types of experiments: FIXED TARGET (FOCUS, SELEX, E791) COLLIDING BEAM (CLEO, CDF, STAR) ACTIVE EXPERIMENT (Super K, SNO) Some Common features: energy/momentum measurement particle identification trigger system data acquisition and storage system software hardworking, smart people… Some Differences: experiment geometry data rate single purpose vs multi-purpose 880.A20 Winter 2002 Richard Kass Fixed Target Experiment Imagine an experiment designed to search for Baryons with Strangeness=+1 These particles would violate the quark model since Baryons always have negative strangeness in the quark model. A candidate reaction is: p-pk-X+ Since this is a strong reaction we need to conserve: baryon number: X has B=+1 strangeness: X has to have +1 electric charge: X has to have Q=+1 General requirements of experiment: we need to know that only k- and one other particle produced in final state To achieve this we will have to: get a beam of p-’s with well defined momentum (we need an accelerator) get a target with lots of protons (e.g. liquid hydrogen) identify p-’s and k-’s eliminate background reaction: p-p p-p measure the momentum of the p-’s and k-’s eliminate background reactions: p-pk-k+n or k-kop a way to record the data 880.A20 Winter 2002 Richard Kass Simple Quark Model 1960’s Quarks are point-like spin ½ objects. Quarks “feel” the strong force, in addition to EM, Weak, and Gravitational forces. Mesons: pair of quark and anti-quark Baryons: triplets of quarks 880.A20 Winter 2002 d u s c b t Electric charge -1/3 2/3 -1/3 2/3 -1/3 2/3 Isospin Iz -1/2 +1/2 0 0 0 0 strangeness 0 0 -1 0 0 0 charm 0 0 0 +1 0 0 bottom 0 0 0 0 -1 0 topness 0 0 0 0 0 +1 Richard Kass Example of fixed target experiment: FOCUS Momentum: silicon+drift chambers+PWC’s+magnet Energy: EM+hadronic calorimeters Particle ID: Cerenkov Counters, muon filter calorimeter Real life view 880.A20 Winter 2002 Richard Kass CLEO III Experiment General purpose detector to study lots of different final states produced by e+e- annihilations at 10 GeV cm energy e+e-B+B- B+*+ B-D*0pD*0 D0g m+mD0 K- p+ *+s0p+ s0 p+p- Must have cylindrical geometry since beams pass through the detector Must measure: momentum of charged particles energy of g’s and po’s Must identify particles: charged: e, m, p, k, p neutral: g, p0, k0, L 880.A20 Winter 2002 Richard Kass Example of active experiment: SuperKamiokande Original purpose of experiment was to search for proton decay: pe+p0 Baryon and lepton number violation predicted by many grand unified models (e.g. SU(5)) General Requirements for experiment Need lots of protons (decay rate of 1032 years7x103 tons of H2O) Size: Cylinder of 41.4m (Height) x 39.3m (Diameter) Weight: 50,000 tons of pure water Need to identify e-’s and p0’s Reject unwanted backgrounds (cosmic rays, natural radiation) 103m underground at the Mozumi mine of the Kamioka Mining&Smelting Co Kamioka-cho, Japan Inside SuperK 880.A20 Winter 2002 Richard Kass Super Kamiokande Closer look at experimental requirements: Identifying p’0s tricky since p0gg thus must identify g’s Need to measure energy or momentum of e and p0 impractical to use magnetic field measure energy using amount of Cerenkov light detect cerenkov light using photomultiplier tubes 11,200 photomultiplier tubes, each 50cm in diameter , the biggest size in the world Energy Resolution: 2.5% @ 1 GeV and 16% (at 10 MeV) Energy Threshold: 5 MeV Need to measure direction of e and po to see if they come from common point cerenkov light is directional Need to measure timing of e and po to see if they were produced at common time cerenkov light is “quick”, can to timing to few nanoseconds BUT DON’T FORGET CIVIL ENGINEERING! Nov 12: accident destroys 1/3 of phototubes Nov. 13: Bottom of the SK detector covered with shattered PMT glass pieces and dynodes. 880.A20 Winter 2002 Richard Kass Particle Detection In order to detect a particle it must interact with matter The most important “detection” processes are electromagnetic Energy loss due to ionization electrons particles heavier than electrons (e.g. m, p, k, p) Energy loss due to photon emission Hadrons (p,k,p) interact with matter bremsstrahlung (mainly electrons) via the strong interaction and create Interaction of photons with matter particles through inelastic collisions. photoelectric effect These particles lose their energy via Compton effect EM processes: pair production (g e+e-) p0ggor p+m+n,m+e+nn Coulomb scattering (multiple scattering) Other/combination of electromagnetic processes cerenkov light scintillation light electromagnetic shower transition radiation Calculation of above processes involve classical EM and QED 880.A20 Winter 2002 Richard Kass