I have always wondered how they can detect these particles, as anything around the size of a quark or smaller has not been measured and is purely theoretical.
An electron, the first elementary particle discovered, has no discernible size, and is considered to have none in principle. It’s not that it has ZERO size, understand, it’s just that size is not one of its properties.
Well you might wonder! There was a time when a particle was a particle, and the discovery of the positron is documented by a single photgraph of its track in a cloud chamber.
In the seventies, new particles such as the J/psi ( don’t ask ) were detected by a “resonance”, where the particle is created at a certain energy of interaction and decays instantly into detectable ( known ) particles. So it reveals itself as a “bump” in the graph of particle production versus energy.
This same idea carries into the detection of the Higgs boson, except that here it is at very high energy ( of course ) and is represented by a very faint signal. The interactions are detected by the billions and sent through data processing which sorts them according to various characteristics which leave a handful of candidates. Now it is up to the statistics to decide whether this handful is within random deviation, or so many sigmas beyond it.
Of course, it was determined that it was beyond chance, but it is still a detection of the most subtle and abstract kind - well beyond the “bumps” of the seventies. So that’s where we stand.