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Advanced Physics Laboratories

       
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Muon Decay

ABOUT THE EXPERIMENT
The muon is a heavy unstable version of the electron, with mass mm= 105.6 MeV/c2 and lifetime tm ~ 2.1 msec. The decay m g e ne nm, or "muon beta decay"  is one of the simplest manifestations of the weak interaction. Particle production from the rain of cosmic rays on the upper atmosphere creates a muon flux of approx. 100/m2-s at sea level. In this experiment we use a photomultiplier in a tank of liquid scintillator to detect cosmic ray muons, and to time the delay between stoppage of a cosmic ray muon and appearance of its decay electron. The distribution of muon lifetimes has an exponential form characteristic of radioactive decay; the lifetime is extracted and compared to expectations for the universal weak interaction.
WHAT YOU WILL LEARN
  • Cosmic Rays
  • Muons and the Weak Interaction
  • Scintillators, photomultipliers, NIM electronics for fast timing measurments, computer controlled ADC and histogramming with the Amptek "Pocket MCA"
PREPARATION
  • If you are completely unfamiliar with the tools of scintillator detection, you may want to do the Gamma-Ray Spectroscopy experiment before trying Muon Lifetime.
  • Required reading:
    • "Measurement of the Muon Lifetime", 441-442 Write-up (PDF) and references therein.
  • Recommended reading: 
    • http://pdg.lbl.gov/2001/cosmicrayrpp.pdf (Particle Data Book entry on cosmic rays)
    • Fraunfelder and Henly, Subatomic Physics, Chap 11 (Weak Interaction), Chapter 19 (Cosmic Rays)
    • G.F.Knoll, Radiation Detection and Measurement, Chap 2,8,9,16, 17
OTHER DOCUMENTATION