Richard Kass
Physics 780.02
Muon Lifetime Report
Your muon lifetime report should include the following items:
1) A complete diagram of the setup used to measure the muon lifetime. Include a logic diagram that shows the combination of signals that were used for veto, start, and stop.
Include all delays used to insure the proper timing of the signals.
2) A plot of your data (actually a histogram) of time (nsec) vs counts/50nsec. Note: each data bin represents a 50nsec time interval.
3) The calculated muon lifetime and its error (standard deviation) from your data. In case you need a hint as to how to calculate the lifetime and its error from your data see example 4.8
(p107) of “Techniques for Nuclear and Particle Physics Experiments”, 2 nd edition, by W. R.
Leo.
4) A comparison of your measured muon lifetime with the accepted value. The PDG book has the current value of the muon lifetime.
5) Suppose that in addition to the muon your data also contains a particle with similar characteristics as the muon but a lifetime of 4  sec. Estimate how many of such particles could be in your data sample.
6) Look at the derivation of the muon lifetime in “Introduction to Elementry Particles” by
Griffiths, Section 10.2 (p304). What value of the muon lifetime do you get using equation
10.39? The tau (  ) lepton is a more massive version of the electron and muon:
electron mass 5.1x10
-4
muon mass 1.06x10
GeV/c
-1
tau mass 1.78 GeV/c 2
2
GeV/c 2
Using the muon lifetime as an example estimate the lifetime of the tau lepton. Note: unlike the muon the tau is massive enough to decay into many final states. So, first estimate the branching ratio of a tau into an electron (this is done similar to the B meson to electron branching ratio we calculated in class) and then relate this branching ratio for tau decay to electron (BR(  e)) and the rate for tau decay to electron (  (  e)) to the lifetime using:
Lifetime=BR(  e)/  (  e)