Fragmentation of Quark and Gluon Jets in Proton-antiproton Collisions at Center-of-mass Energy of 1.8 TeV

Book excerpt: ABSTRACT: We report the first model independent measurement of charged particle multiplicities in quark and gluon jets, Nq_ and Ng_, produced at the Tevatron in proton-antiproton collisions with center-of-mass energy 1.8 TeV and recorded by the Collider Detector at Fermilab. The measurements are made for jets with average energies 41 and 53 GeV by counting charged particle tracks in cones with opening angle of thetac_=0.28, 0.36, and 0.47 rad around the jet axis. The corresponding jet hardness Q=Ej_et*thetac_ varies in the range from 12 GeV to 25 GeV. At Q=19.2 GeV, the ratio of multiplicities r=Ng_/Nq_ is found to be 1.64"0.17, where statistical and systematic uncertainties are added in quadrature. The results are in agreement with re-summed perturbative QCD calculations and are consistent with recent ee− measurements.