Discuss the below:
Four Momentum in Different Frames
Q: A pion of mass m moves with a speed u in the positive y direction in frame S with parametrs BETAu = u/c and GAMMAu = (1 - BETAu^2)^-1/2. The pion decays into two gammay rays. An observer S' moves in the positive x direction with speed v = (BETA)(c) [this is a different BETA and GAMMA than before] and detects the two photons.
A. Compute the sum of the x components of momentum in S' for the photons.
B. Compute the combined energy of the two photons in S'.