Is it possible that there are particles smaller than quarks?
As various points in history, we've made conclusions that had eventually been proven incorrect. Is there a physical law that disallows particles smaller than quarks to exist? If so, does this size come from math in the Planck scale?
Answers ( 1 )
This question is not as simple as it sounds. First you have to decide what you mean by "smaller".
By convention, unless we can "see" internal structure and/or components of a particle (by scattering other particles off it and looking at the scattering distribution) we treat it provisionally as a "point particle" -- i.e. it has no "size"; it is a point. Quarks are points, as far as we can tell.
Alternatively, you may be asking about the particle's rest mass m. In that case there are several particles "smaller" (i.e. lighter) than quarks: electrons, neutrinos and their respective antiparticles; also photons and gluons, which (as far as we can tell) have no mass.
If you want to go back to "size" as in physical dimensions, even point particles have a Compton wavelength, which would serve as a measure of their effective extent in space. But the Compton wavelength is inversely proportional to the mass, so heavy particles are smaller than lighter particles.
Weird, huh?