A particle detector can be used to measure the speed of an unstable particle if the lifetime is known. Particle 'X' has mean lifetime 7 in its rest frame. Suppose 'X' particles are created in an experiment inside the detector by a nuclear reaction. If the 'X' particles leave tracks with mean length L before they decay into other particles, what is the mean speed of the 'X' particles? Express the answer in terms of the speed of light. T = 257.1 ps; L = 11.3 cm;

A particle detector can be used to measure the speed of an unstable particle if the lifetime is known. Particle 'X' has mean lifetime 7 in its rest frame. Suppose 'X' particles are created in an experiment inside the detector by a nuclear reaction. If the 'X' particles leave tracks with mean length L before they decay into other particles, what is the mean speed of the 'X' particles? Express the answer in terms of the speed of light. T = 257.1 ps; L = 11.3 cm;