Study of four-jet events and evidence for double parton interactions in pp-bar collisions at sqrt s =1.8 TeV.

Abstract

Kinematic properties of four-jet events produced in $p\overline{p}$ collisions at $\sqrt{s}=1.8$ TeV have been studied using data with an integrated luminosity of 325 ${\mathrm{nb}}^{\ensuremath{-}1}$ collected using the Collider Detector at Fermilab during the 1988-1989 Fermilab Collider run. The individual jet ${p}_{T}$ spectra and the angles between each jet pair are compared to the predictions of leading-order quantum chromodynamics for the double gluon bremsstrahlung process and good agreement is observed. In addition, a search for double parton scattering has been undertaken using variables sensitive to the topology of four-jet events. A small double parton content provides the best description of the data. We find $\frac{{N}_{\mathrm{DP}}}{{N}_{\mathrm{DB}}}={5.4}_{\ensuremath{-}2.0}^{+1.6}%$, where $N$ represents the number of events attributed to each process. We measure ${\ensuremath{\sigma}}_{\mathrm{DP}}={63}_{\ensuremath{-}28}^{+32}$ nb for jets having ${p}_{T}g25$ GeV/c in the pseudorapidity interval $|\ensuremath{\eta}|l3.5$.