In the four momentum treatment of relativistic particle collisions or decays, The mass of a particle is different for various observers. O Momentum and energy are still conserved in any inertial frame of reference. O The energy equals the sum of the momentum, pc, plus the mass, mc2. O The momentum and energy for a process are the same in all frames of reference.

In the four momentum treatment of relativistic particle collisions or decays, The mass of a particle is different for various observers. O Momentum and energy are still conserved in any inertial frame of reference. O The energy equals the sum of the momentum, pc, plus the mass, mc2. O The momentum and energy for a process are the same in all frames of reference.