In: Physics
There are a whole zoo of subatomic particles that have very short lifetimes before decaying. The pion, also called the ? meson, has a proper mean lifetime of 2.6 × 10?8 s.
(a) Explain what is meant by the “proper time.” What frame will measure the proper time?
(b) If a beam of pions has a speed of 0.9c, how far will they travel (on average, decay is a random statistical process) in the laboratory frame before they decay?
(c) If the number of pions in a sample is given by A0 e ?t/? , where ? is the lifetime and A0 is the number of pions you started with, what fraction of the pions are left after traveling 20 m in the laboratory frame?