Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Simple question regarding annihilaion

  1. Oct 12, 2010 #1
    if annihilation of particles(let's say proton-antiproton) releases x energy at 2 giga electron volts, then if we annihilate it at let's say 4 GeV, would we be getting double the energy?

    also, i have seen the wikipedia page of annihilation of proton and antiproton which mentions the energy levels at 2 GeV but does not mention released energy at rest "clearly"....please help
  2. jcsd
  3. Oct 12, 2010 #2


    User Avatar
    Science Advisor

    The calculation is simplified in the c.m. system; proton and anti-proton have energy-momentum (E, p) and (E, -p). The sum ist (2E, 0), so 2E is the c.o.m energy. Of course E and p are related via E² - p² = m² where m is the rst mass m=938 MeV.
  4. Oct 12, 2010 #3
    Re: Simple question regarding annihilation

    If one could cause an annihilation with both particles at rest, the result is simply twice the rest mass energy (2*938 MeV ~2 GeV). However experimentally you send two streams of particles at some velocity toward each other, so the momentum at annihilation is not zero (rest momentum) and contributes to the total energy.
  5. Oct 14, 2010 #4
    Thanks for the answers.....but please try to explain in layman terms.....I'm not a physicist by profession here....just doing my b.s in Computer science.....I don't get the c.m system......
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook