quantum mechanics - Maximizing particle annihilation of a certain particle type?

Is there any theoretical situation where one would be able to maximize the production of a certain type of particle?

I wish to continue discussing this question: Where would dark matter be produced? . Kyle Oman gave an excellent answer, which lead me to the next question, this time about particle physics (field I am weak in):

Question

If we have the hypothetical reactions:

$e^+ + e^- \rightarrow Z + Z$

$e^+ + e^- \rightarrow X + X$

$e^+ + e^- \rightarrow Y + Y$,

where $e^+$, $e^-$ are positron and electron, and $Y$, $X$, $Z$ are some particles. Assume a large amount of $e^+$, $e^-$; would it be possible to create a theoretical situation where $e^+ + e^- \rightarrow X + X$ production is maximized based on the particle $X$ properties and e.g. momentum of $e^+$, $e^-$, while not maximizing the production of $Y,Z$?

I would appreciate sources/further reading, and if the question is too general I can modify it.