Anti-proton pair production and the bevatron?

Crucifix

I've been trawling the net for hours, and just can't find a good explanation of the process. How exactly does a collision of two protons at an energy of 6.2GeV cause pair production? I'd really appreciate any insights.

Woden

/me digs up dregs of particle physics course.

i'm sure planck2 can give you something more comprehensive later

anyway its possible to create particle (e.g like pair production) by slamming other particles into each other, when you slam them together at higher energies you have more available energy to make the particles. energy being mass due to the whole einstein thingy.

so to create a pair of electrons for example of rest mass 0.5 MeV (or whatever it is) you need over 1 MeV of available energy in the centre of mass frame of the system. one of the reasons its pair production is related to conservation of lepton number in that you can't just produce one electron. you produce an electron anti electon pair (pair production) which retains the over all lepton number before and after the collison.

a small point to note is that although they say they are smashing protons together they aren't really its the quarks that hit each other

hope this helps a bit, it makes me realise how hand wavy the stuff i know is anyway

data

Crucifix

So if a collision between a fast moving proton and a stationary object causes pair production, is it as simple as the kinetic energy of the proton being changed into an antiproton?

planck2

No. What happens is this: there are two types of set up for this experiment, the colliding beam set up, as is the case in circular accelerators, ie both high energy proton beams are going around the collidor and they smash into each other . This is the best set up in most cases as the centre of mass energy is highest. What happens is this, there is a range of energies allowed for the creation of particle/anti-particle production due to the set up of the experiment. And the protons and anti-protons are smacking into each other and can penetrate into each other so this kind of stretches each proton/ anti- proton apart. however we are coming to the guts of your question, you see protons and anti protons are made up of quarks which are held together by high energy strings in a sense called gluons. Now experiments have shown that if you try to stretch a gluon, i.e. try and seperate two attached quarks, the gluon doesn't break, what happens is that a particle/anti-particle pair is created for a while. So if we start stretching a gluon holding two quarks together we start getting new particle pairs once we've stretched the gluona certain amount. The other uses a stationary target, but the idea is the same

Ali Cat

I probably just misunderstood your question but in pair production the charge must be conserved so the energy can't just be changed into an anti-particle, a fundamental law would be broken.

planck2

see my answer