Measurement of Dijet Angular Distributions by the Collider Detector at Fermilab

We have used $106{\mathrm{pb}}^{-1\mathrm{}}$ of data collected in $p\overline{p}$ collisions at $\sqrt{s}=1.8\mathrm{}\mathrm{TeV}$ by the Collider Detector at Fermilab to measure jet angular distributions in events with two jets in the final state. The angular distributions agree with next to leading order predictions of QCD in all dijet invariant mass regions. The data exclude at 95% CL a model of quark substructure in which only up and down quarks are composite and the contact interaction scale is ${\Lambda }_{\mathrm{ud}}^{+}\le 1.6\mathrm{TeV}$ or ${\Lambda }_{\mathrm{ud}}^{-}\le 1.4\mathrm{TeV}$. For a model in which all quarks are composite the excluded regions are ${\Lambda }^{+}\le 1.8\mathrm{TeV}$ and ${\Lambda }^{-}\le 1.6\mathrm{TeV}$.