Ok, when you use positrons to shoot at stationary electrons in a collider with enough energy so that you make a pair of proton and antiproton. The total energy of the pair would be E = T + MC^2, where M is the total invariance mass of the pair, namely 2*938Mev, or I can use E^2 = (pc)^2 + (Mc^2)^2, and M here is still the invariant mass. I got the correct answer using M = 2 times the mass of the rest mass of a proton, as said previous, 2*938 Mev. What I am trying to understand here is why the invariant mass here is the sum of two masses, when in most cases, invariant mass is not linear, you cant add two masses and conserve the sum.(adsbygoogle = window.adsbygoogle || []).push({});

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Confused about invariant mass in particle collision

**Physics Forums | Science Articles, Homework Help, Discussion**