How can be Calculated the pion mass by using uncertainty principle?

Question

anonymous · Answer

The uncertainty principle might be used to " estimate "the mass of a  pion from its mean lifetime.   This is not necessarily an appropriate use the the principle however.  In this case the uncertainty in energy times the uncertainty in the time it takes to measure this energy is less than or equal to Planck's constant divided by 4 Pi.  So given an observed time in this case the mean lifetime you may determine the uncertainty in the total energy of the pion which would be an lower limit of its mass if it were at rest. The mean lifetime is 1.44.. times the half-life of the pion at rest.