1. The problem statement, all variables and given/known data An electron e− and positron e+ moving at the same speed in the Earth reference frame collide head-on and produce a proton p and an antiproton p¯. The electron and positron have the same mass. The proton and antiproton also have the same mass. The mass of the proton is 1836.15 times the mass of the electron. Calculate, in the Earth reference frame, the minimum value possible for the ratio of the electron's kinetic energy to its internal energy in order to have the reaction e− + e+ →p + p¯ take place. Want: K/E_internal = ??? 2. Relevant equations K = (y-1)mc^2 --- y = lorentz factor E_internal = mc^2 3. The attempt at a solution I'm not even remotely sure what this question is asking. Can someone offer me some guidance?