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(a) Calculate the distance it travels before decaying. (b) If the two photons em

ID: 1324619 • Letter: #

Question

(a) Calculate the distance it travels before decaying.

(b) If the two photons emitted travel along the x axis, what are their speeds?

One of the decay modes of the no produces two photons. M pi o = 135.0 MeV/c^2 mean lifetime = 8.4x10^-15 s The pion is moving at 0.8c in the +x direction relative to the detector in the lab. (e) If the photons travel along the y axis, determine the 4-momenta for each one. (f) Using your answer to (e), write the 4-momenta for the photons if they travel along the x axis. (g) Transform your answer to (f) to a frame where the pion is moving at 0.8c in the +x direction. n degree = gamma + gamma

Explanation / Answer

The life time of pion with respect to earth is

t = t / sqrt ( 1 - ( v /c )^2 )

t = (8.4*10^ -15 s ) / sqrt ( 1 - ( 0.8c/c)^2 )

= 1.4*10^ -14 s

distance travelled by the pion is

d = v t

= ( 0.8) ( 3*10^ 8 m/s ) ( 1.4*10^ -14 s )

= 3.36*10^ -6 m

b)

since the photons are mass less particle, the speed of phtotons iis equal to the speed of light. c.