“In recent years several new particles have been discovered which are currently assumed to be “elementary,” that is, essentially structureless. The probability that all such particles should be really elementary becomes less and less as their number increases. It is by no means certain that nucleons, mesons, electrons, neutrinos are all elementary particles.” -Enrico Fermi
The Standard Model of particle physics — with its six quarks in three colors, its three generations of charged leptons and neutrinos, the antiparticle counterparts to each, and its thirteen bosons, including the Higgs — describes all the known particles and their interactions in the Universe. This extends to every experiment ever performed in every particle accelerator. In short, this is a problem: there’s no clear path to what new physics lies beyond the Standard Model.
So physicists are looking for any possible anomalies at all, at any theoretical ideas that lead to new predictions at the frontiers, and any experimental result that differs from the Standard Model predictions. Unfortunately, we’re looking at thousands of different composite particles, decays, branching ratios, and scattering amplitudes. Our standards for what’s a robust measurement and a compelling result need to be extremely high.