Recent content by chem_heather

Hmm, I just found this on another thread: "Since m=0, combining those two gives the four-momentum of a photon as: (|p|,p) or equivalently for a photon traveling in the x direction: (E/c,E/c,0,0)" So, if that's the case, the 4-vector for the lab-frame before the collision would be P = (c(p1 +...

That's where I'm getting confused. Would the 4-vector for the lab frame before the collision be P = (0,c(p1 + p2),0,0)? I used 0 in the A0 spot because the photons don't have any rest-mass. And for the center-of-mass frame after the collision be P'cp = (2mec2,0,0,0)? When I use these, P2 = 25...

Homework Statement Consider two photons, one with energy ε1 = 2MeV traveling to the right, and the other with energy ε2 = 3MeV moving tot he left. The two photons collide head-on and produce a positron-electron pair. Suppose the the electron and positron move along the same axis as the photons...