Measurement of Dijet Angular Distributions at CDF

TL;DR

This study measured dijet angular distributions in proton-antiproton collisions at 1.8 TeV, confirming QCD predictions and setting limits on quark substructure models with compositeness scales up to 1.8 TeV.

Contribution

First measurement of dijet angular distributions at Tevatron energies confirming QCD and constraining quark compositeness models.

Findings

Angular distributions agree with NLO QCD predictions.

Excluded quark substructure models with compositeness scales below 1.8 TeV.

Set 95% confidence level limits on contact interaction scales.

Abstract

We have used 106 pb^-1 of data collected in proton-antiproton collisions at sqrt(s)=1.8 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 (NLO) predictions of Quantum Chromodynamics (QCD) in all dijet invariant mass regions. The data exclude at 95% confidence level (CL) a model of quark substructure in which only up and down quarks are composite and the contact interaction scale is Lambda_ud(+) < 1.6 TeV or Lambda_ud(-) < 1.4 TeV. For a model in which all quarks are composite the excluded regions are Lambda(+) < 1.8 TeV and Lambda(-) < 1. 6 TeV.