Eli5: why is there a lot of matter but no antimatter if they both appear simultaneously?

Question

Eli5: why is there a lot of matter but no antimatter if they both appear simultaneously?

In: Physics

Answer 1

There had to have been some ‘process’ in the early universe that treated matter different from antimatter. We actually already know of such a process (namely some part of the weak nuclear interaction) but the difference it creates between matter and antimatter is not large enough to explain how much more matter than antimatter there is in the universe. This means there has to be some other process that we don’t know of that is responsible.