Particle clusters seem to occur at exponents of baseline energies for what we consider to be ordinary particles. The exotic particles we've found have been at the higher end.
If you look at the early work by Dr. Jay Phippen, you'll see the intentional constraints he places on the pair production is the solution set to 12 (actually, 11, one was an identity) Feynman-Dyson diagrams. I believe his thesis is on file at Utah State University. The initial computations were done at Los Alamos labs, back with the CDC Cyber was "hot stuff". During the mid 1980's, when he was my mentor, I ported his software and the matrix math for him to Sun Microsystems equipment, and he was able to reproduce the results, which got us really, really close to the predicted mass of the W particle.
It also let us tweak things substantially, trying a lot more Monte Carlo collision simulations in a shorter period of time, and given that the new hardware was capable of representing much larger numbers, it allowed the extension of the test energy rangers much higher (into the Higgs arena, and beyond).
FWIW, the collisions were simulations of relativistically invariant P-P and P-N collisions using the Berkeley Physics package, and the produced particle pairs were further constrained by the physics after they were produced (i.e. energy, angle, and so on as to what counted as an "allowable" pair).
I believe you can also find some references to it through my other faculty advisor, Dr. Robert Capener's work, although he abandoned his involvement in the U.S. atomic weapons program shortly after the neutron bomb was created, and concentrated mostly on CS after that.
So I think it's improbable that we have seen our last new particles.