Jeff Tseng

Abstract:

The growth and development of “charged particle jets” produced in proton-antiproton collisions at [Formula Presented] are studied over a transverse momentum range from [Formula Presented] [Formula Presented] to [Formula Presented] [Formula Presented] A variety of leading (highest transverse momentum) charged jet observables are compared with the QCD Monte Carlo models HERWIG, ISAJET, and PYTHIA. The models describe fairly well the multiplicity distribution of charged particles within the leading charged jet, the size of the leading charged jet, the radial distribution of charged particles and transverse momentum around the leading charged jet direction, and the momentum distribution of charged particles within the leading charged jet. The direction of the leading “charged particle jet” in each event is used to define three regions of [Formula Presented] space. The “toward” region contains the leading “charged particle jet”, while the “away” region, on the average, contains the away-side jet. The “transverse” region is perpendicular to the plane of the hard [Formula Presented]-to-[Formula Presented] scattering and is very sensitive to the “underlying event” component of the QCD Monte Carlo models. HERWIG, ISAJET, and PYTHIA with their default parameters do not describe correctly all the properties of the “transverse” region. © 2002 The American Physical Society.

Abstract:

We present a measurement of the cross section and the first measurement of the heavy flavor content of associated direct photon + muon events produced in hadronic collisions. These measurements come from a sample of 1.8 TeV pp̄ collisions recorded with the Collider Detector at Fermilab. Quantum chromodynamics (QCD) predicts that these events are primarily due to the Compton scattering process cg→cγ, with the final-state charm quark producing a muon. The cross section for events with a photon transverse momentum between 12 and 40 GeV/c is measured to be 46.8±6.3±7.5 pb, which is two standard deviations below the most recent theoretical calculation. A significant fraction of the events in the sample contain a final-state bottom quark. The ratio of charm to bottom production is measured to be 2.4±1.2, in good agreement with QCD models.

Abstract:

The inclusive cross section for J/Ψ production times the branching ratio B(J/Ψ→μ ⁺ μ ^- ) has been measured in the forward pseudorapidity region: B×dσ[p ^- +p→J/Ψ(p T >10 GeV/c,2.1<|η|<2.6)+X]/dη = 192±9(stat) ±29(syst) pb. The results are based on 74.1±5.2 pb ^-1 of data collected by the CDF Collaboration at the Fermilab Tevatron Collider. The measurements extend earlier measurements of the D0 Collaboration to higher p T ^J/Ψ . In the kinematic range where the experiments partially overlap, these data are in good agreement with previous measurements.

Abstract:

We present measurements of the B⁺meson total cross section and differential cross section dσ/dpT. The measurements use a 98±4 pb^-1sample of pp̄ collisions at √s=1.8 TeV collected by the CDF detector. Charged B meson candidates are reconstructed through the decay B^±→J|ψ^±with J|ψ→µ⁺µ^-. The total cross section, measured in the central rapidity region |y|<1.0 for pT(B)>6.0 GeV/c, is 3.6±0.6(stat ⊕ syst) µb. The measured differential cross section is substantially larger than typical QCD predictions calculated to next-to-leading order.