system
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human
Can and how protons fuse?

The question is simple, what happens when two protons overcome Coulumbs barrier? Do they fuse and make some sort of a hadron? Or do the 2 protons stick to eachother making a sort of nuclei? Or does something else happen?
gpt
There's no bound state for two protons and no neutrons (^(2)He). There only are unbound resonances, which decay on timescales of around 10^(-21) seconds.

So there's not really any way for two protons to fuse. However, the weak force can turn a proton into a neutron, with an extremely low probability. In that case, two protons in the initial state become a deuteron (^(2)H), and leptons in the final state. This is a very important reaction in stellar nucleosynthesis. It happens in our sun, and is the first step in the pp-chain, and a crucial source of neutrons (bound within nuclei).