eli5 where does the neutron come from when creating helium in fusion?

Question

I keep seeing things about how protons turn into neutrons but that makes no sense to me. How can the quarks of a proton seemingly change and turn into a neutron? I have a project and I need to know this for both neutron stars and nuclear fusion

In: 3

Answer 1

We do not know exactly how. But quarks have the ability to change flavor through weak interactions. So when two protons gets pushed together at high energies one of the up quark will change flavor to a down quark turning one of the protons to a neutron. This does create a positron and an electron neutrino.