What determines what kind of particles will specific particle collision produce?
Sunday, January 22nd, 2012 at
7:00 pm
For example, what makes proton-proton collision to produce a neutrino, positron and a deuteron?
@misticshakra: If you don’t understand it, there is no need to answer this question.
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The imagination of the physicist. It’s mathematical BS.
Conservation laws. It’s all about conserved quantities. For example, in beta decay, charge and lepton number is conserved, so a neutron decaying must give both a proton and electron (charge), and an electron anti-neutrino (lepton number).
Furthermore, energy conservation is a big one. A collision of two protons (mass = 983 MeV) at an energy of 5 GeV cannot produce a 10 GeV particle.
There are a bunch of these conservation laws, energy, charge, lepton number, baryon number, color, … But also some more abstract ones like parity.
Also, in the example you stated, you start off with two protons (charge +2, Baryon number +2). The end result has:
1 electron neutrino — charge 0 — electron lepton number +1
1 positron —————- charge 1 — electron lepton number -1
1 proton ——————- charge 1 — baryon number +1
1 neutron —————— charge 0 — baryon number +1
There are usually multiple options for each interaction, called decay channels. Which it ends up with is a matter of statistics, and calculating the probabilities of each can be done with the full machinery of the Standard Model.
It’s also usually a function of energy. For example, when an electron and positron collide just above the rest energy of a Z boson, most decays will be into a Z boson. This is called a resonance.
There’s a lot to be said about this, and a little Yahoo Answers box can’t do it justice.