Comment by agaminon22 on 21/11/2024 at 18:50 UTC

67 upvotes, 3 direct replies (showing 3)

View submission: What causes the mutual annihilation of matter-antimatter reactions?

First of all, antimatter and matter don't always have to annihilate. Sometimes they can collide and scatter, look up Bhabha scattering. This is the process by which an electron and a positron scatter elastically, not annihilating. Furthermore, annihilation is not necessarily always into photons, it can lead to oher particles, such as neutrinos.

What I'm trying to point towards is that these kinds of fundamental reactions happen probabilistically and only when no conservation laws are broken. But if no conservation laws are broken, that essentially implies that they *will* happen. When matter and antimatter collide, there is no conservation law being broken through annihilation, and therefore it's a possible process that will happen. At low energies, it's the dominant process.

If you think about it in terms of quantum numbers, with positrons and electrons for example, the charges are opposed to form a state of zero change. The lepton quantum number is also zero. Essentially it's all lined up to form particles of zero charge, without lepton number, with the appropiate spin: photons. But you can also produce two neutrinos (a neutrino and an antineutrino), or really any other compatible possibility.

Replies

Comment by Krail at 21/11/2024 at 22:58 UTC

24 upvotes, 4 direct replies

I'm still confused about why annihilation happens. Is it just that opposite charges want to equalize to zero?

Comment by mesouschrist at 23/11/2024 at 20:30 UTC

2 upvotes, 0 direct replies

Great answer. Neutrinos wouldn't be my first example of other particles that can be created. e+e- ->neutrinos is exceedingly rare at low energy and essentially experimentally unprovable at high energies. On the other hand, when a proton and an antiproton collide they make typically 3-6 pions (charged and uncharged, of course with the total charge in the end equaling the total charge in the beginning)

Comment by holiestMaria at 21/11/2024 at 18:57 UTC

1 upvotes, 0 direct replies

Thank you! I understand now that matter-antimatter reactions are much more complicated.