Can someone explain to me like I am a dumb fucking retard, which I am, where the fuck does the energy come to turn a proton into a fucking neutron in this reaction :[math]\ce{p + p \rightarrow d + e^+ + \nu_e}[math]I know that the interaction balance out in the end because of the binding energy of the deuteron that gets released, but while the deuteron doesn't fucking exist yet, an Up quark has to turn into a Down quark, which is heavier, so where the fuck does the energy come from if it isn't released yet.
>>16919287you’re thinking about it like the up quark has to "pay" the mass difference before anything else happens, but that’s not how the reaction works. the process is one single quantum transition from two protons to a deuteron plus a positron and a neutrino. energy conservation applies to the whole initial and final states, not to some imaginary halfway point. the total mass-energy of two free protons is higher than the total mass-energy of the deuteron plus the emitted particles, and that difference covers everything, including the u -> d conversion
>>16919289So that Feynman diagram is just one contribution to the amplitude of the interaction and doesn't mean anything beside "most probable virtual stuff that happen internally but could be anything else" ?
>>16919577yes that's it. a feynman diagram is just one term in the perturbative expansion of the total quantum amplitude, it's not a literal sequence of physical events happening in time.the internal lines W+ do not represent real particles with well-defined energies, so there is no stage where a quark must “pay” a mass difference first. only the total initial and final states must satisfy energy conservation.
