I'm struggling a bit with my module on particle physics. This is only part of the problem set, but I need it for the rest (which is asking whether or not some particular decays are possible). My problem is: How can you tell which is the most likely interaction for certain processes? For example, a positron and electron annihilating and producing a quark anti-quark pair; the quark pair then goes on to hadronize. I'm not really sure which are the most likely processes responsible but my guess is: weak for the first part, strong for the second part. Is is possible that the second part is also weak? Also, am I right in saying that processes that go via the strong force have to conserve strangeness, but ones that go via weak do not have to? Any help would be much appreciated, Thankyou!