Are Quarks Fundamental?

With the current generation of accelerators, we have found no evidence for structure or constituents within quarks. One way to look is to collide protons head-on at extremely high energies. If quarks had smaller constituents inside them, the resulting particles would more often fly out at larger angles.

So far, the study of these collisions establishes that the quark is fundamental to a tiny scale, 10^-19 meters.

But one does not know if quarks are fundamental. Only future investigations through experiments at new, more energetic colliders will reveal this secret of nature.