The Dijet Mass Spectrum and a Search for Quark Compositeness in bar{p}p Collisions at sqrt{s} = 1.8 TeV

Abstract

Using the DZero detector at the 1.8 TeV pbarp Fermilab Tevatron collider, we have measured the inclusive dijet mass spectrum in the central pseudorapidity region |eta_jet| < 1.0 for dijet masses greater than 200 Gev/c^2. We have also measured the ratio of spectra sigma(|eta_jet| < 0.5)/sigma(0.5 < |eta_jet| < 1.0). The order alpha_s^3 QCD predictions are in good agreement with the data and we rule out models of quark compositeness with a contact interaction scale < 2.4 TeV at the 95% confidence level.

Figures (4)

• Figure 1: $d^{3} \sigma / d \hbox{$M$} d \eta_{1} d \eta_{2}$ for $\hbox{$\mid \! \eta_{\rm jet} \! \mid$}<1.0$. The DØ data are shown by the solid circles, with error bars representing the $\pm$$1\sigma$ statistical and systematic uncertainties added in quadrature (in most cases smaller than the symbol). The histogram represents the jetrad prediction.
• Figure 2: The correlations between systematic uncertainties in bins of dijet mass (see Table \ref{['table_1']}) for $\hbox{$\mid \! \eta_{\rm jet} \! \mid$}<1.0$. The correlations are calculated using the average systematic uncertainty. The discontinuities arise from the uncorrelated errors (adjacent to correlations of 1.0) and luminosity matching.
• Figure 3: The difference between the data and the prediction ( jetrad) divided by the prediction for $\hbox{$\mid \! \eta_{\rm jet} \! \mid$} < 1.0$. The solid circles represent the comparison to the calculation using CTEQ3M with $\mu = 0.5 \hbox{$E_{T}^{\rm max}$}$. The shaded region represents the $\pm$$1\sigma$ systematic uncertainties. The effects of changing the renormalization scale and choosing a different pdf are also shown (each curve shows the difference between the alternative prediction and the standard prediction).
• Figure 4: The ratio of cross sections for $\hbox{$\mid \! \eta_{\rm jet} \! \mid$}<0.5$ and $0.5<\hbox{$\mid \! \eta_{\rm jet} \! \mid$} <1.0$ for data (solid circles) and theory (various lines). The error bars show the statistical and systematic uncertainties added in quadrature, and the crossbar shows the size of the statistical error.