Measurement of QCD jet broadening inpp¯collisions ats=1.8TeV

A measurement of the QCD jet-broadening parameter $〈Q_T〉$ is described for high-$E_T$ jet data in the central calorimeter of the Collider Detector at Fermilab. As an alternate approach to clustering analysis, this method involves the use of a global event parameter which is free from the ambiguities associated with the definition and separation of individual clusters. The parameter $Q_T$ is defined as the scalar sum of the transverse momentum perpendicular to the transverse thrust axis. Parton-level QCD predictions are made for $〈Q_T〉$ as a function of $E_T$, the total transverse energy in the events, and suggest that a measurement would show a dependence on the running of the strong coupling constant ${\alpha }_s$. Comparisons are made to first-order QCD parton-level calculations, as well as to fully evolved and hadronized leading-log simulations. The data are well described by the QCD predictions.