# Basic Measurements: What do we want to measure What Makes Particle Detection Possible

## Basic Measurements: What do we want to measure What Makes Particle Detection Possible

Farber, Stephen, Film Critic has reference to this Academic Journal, PHwiki organized this Journal Basic Measurements: What do we want to measure Prof. Robin D. Erbacher University of Cali as long as nia, Davis References: R. Fernow, Introduction to Experimental Particle Physics, Ch. 15 D. Green, The Physics of Particle Detectors, Ch. 13 http://pdg.lbl.gov/2004/reviews/pardetrpp.pdf Fundamental Measurements: From Quarks to Lifetimes Fundamental Particle Properties Charge: Charge of a particle can be determined two ways Sign of charge: Direction of deflection in a magnetic field Magnitude of charge: Infer from knowledge of momentum in addition to B-field strength Charge-dependent quantity, such as ionization energy loss, or Ruther as long as d scattering cross section Direction: tracking detectors, B-field Momentum: tracking detectors, B-field Ionization energy loss: sampling w/ scintillation, TOF ( as long as ) (Example: combine from time of flight (TOF) with dE/dx in addition to use Bethe Bloch equation to get charge) Fundamental Particle Properties Mass: Complicated: mainly specialized techniques One Example: Measure two independent mass-dependent quantities: Momentum often one; ionization, range, or velocity Momentum/range: tracking detectors, B-field Ionization/velocity: scintillation, TOF/ dE/dx, C, TOF Example: (Fernow) Use conservation of energy in addition to momentum to measure mass of muon neutrino Use knowledge of mass of pion in addition to muon, in addition to measure momentum in addition to B-field strength accurately Scintillator stops s, magnets guide s, silicon gives momentum v

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Fundamental Particle Properties Mass: Complicated: mainly specialized techniques Second Example: Measure most quantities in an event, reconstruct mass: Jet energies, lepton momenta, missing ET as long as examples Jet energies: em in addition to hadron calorimeters (fragmentation, etc) Momenta: tracking detectors, B-field Missing ET: all of the above, plus missing info & corrections Example: Measure top quark mass from tt pair production events Use best combination (2) of partons to reconstruct top mass to best resolution possible. – Fundamental Particle Properties Spin: Spins complicated as long as decaying particles Ground state particles, electrons in addition to nucleons: Hyperfine structure in optical spectroscopy, atomic/molecular beam experiments, bulk matter measurements using NMR. Other low energy particles: Various techniques eg: charged pions determined by relating the cross section as long as reaction to the cross section as long as the inverse reaction. High energy interactions: Spins can be found from the decay angular distributions, in addition to from the production angular distributions as long as particle interactions. Example: Measure top quark pair spin correlations using angles of decay products. Fundamental Particle Properties Magnetic Moment: Closely related to spin Ground state particles, electrons in addition to nucleons: Again use optical spectroscopy, atomic/molecular beam experiments, bulk matter measurements using NMR. Muons: Original measurement of g-factor done at CERN storage rings including a precise demonstration of relativistic time dilation. Details of these, in addition to current g-2 experiments (BNL) leave as long as homework. Measuring the hyperon: Fermilab protons on beryllium target, s 8% polarized, sent through magnet in addition to spin precession measured, giving , in addition to hence . Keys to measurement: s produced inclusively w/ large cross section, large detector acceptance, high energy long decay length