Measurement of Dijet Angular Distributions at $\sqrt{s}=1.96\mathrm{TeV}$ and Searches for Quark Compositeness and Extra Spatial Dimensions

We present the first measurement of dijet angular distributions in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ at the Fermilab Tevatron Collider. The measurement is based on a dataset corresponding to an integrated luminosity of $0.7{\mathrm{fb}}^{-1}$ collected with the D0 detector. Dijet angular distributions have been measured over a range of dijet masses, from 0.25 TeV to above 1.1 TeV. The data are in good agreement with the predictions of perturbative QCD and are used to constrain new physics models including quark compositeness, large extra dimensions, and ${\mathrm{TeV}}^{-1}$ scale extra dimensions. For all models considered, we set the most stringent direct limits to date.

Figure 1

Normalized differential cross sections in ${\chi }_{\mathrm{dijet}}$ compared to standard model predictions and to the predictions of various new physics models. The error bars display the quadratic sum of statistical and systematic uncertainties. The standard model theory band includes uncertainties from scale variations and PDF uncertainties (see text for details).