You're assuming one can expect the knowledge of chemical reactions to apply to particle interactions, and that is not the case. For example particle accelerato

You're assuming one can expect the knowledge of chemical reactions to apply to particle interactions, and that is not the case. For example particle accelerators can shoot particles against some target one by one, and so there's no need to look at averages. Some interactions never occur, to the best of our measuring ability (i.e. highest energies and number of repetitions). Some others are right away forbidden by laws much stronger than entropy in thermodynamics, in the sense that they're not averages, but mathematical derivations off the symmetries of the universe.