Threshold Kinetic Energy
November 5th, 2022
What is meant by the threshold energy in a particle reaction? If the threshold energy in a particle reaction holds, what can you say about the motion of the particles in the centre of momentum frame? What does this imply about the motion of the particles in the original laboratory frame?
Two photons of energies E1 and E2 collide with their incident directions of motion making an angle theta with respect to each other. The collision annihilates the two photons and produces two new particles of equal rest mass m. Show that at threshold the condition holds:
(E1)(E2)(sin^2(theta/2)) = (m^2)(c^4)