Number 103 (Story #1), November 17, 1992 by Phillip F. Schewe and Ben Stein DO QUARKS HAVE CONSTITUENTS? The issue of quark substructure can be addressed by studying the production of jets of particles in high-energy proton-antiproton collisions. The CDF (Collider Detector at Fermilab) collaboration recently published an analysis of two-jet events produced at the Tevatron collider. Finding no direct evidence, the researchers concluded that any quark substructure would only become evident at energies of 1 TeV or more. (F. Abe et al., Phys. Rev. Lett., 16 Nov.)