D. Benjamin

Measurement of Dijet Angular Distributions by the Collider Detector at Fermilab.

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.

Intercalibration of the longitudinal segments of a calorimeter system

Three different methods of setting the hadronic energy scale of a longitudinally segmented calorimeter system are compared with each other. The merits of these methods have been studied with testbeam data from the CDF Plug Upgrade Calorimeter. It turns out that one of the (commonly used) calibration methods introduces a number of undesirable side effects, such as an increased hadronic signal nonlinearity and trigger biases resulting from the fact that the reconstructed energy of hadrons depends on the starting point of their showers. These problems can be avoided when a different calibration method is used. The results of this study are applied to determine the e/h values of the calorimeter and its segments.

A preshower detector for the CDF Plug Upgrade: test beam results

A preshower detector consisting of plastic scintillating plates with optical-fiber readout was tested at the Fermilab meson beamline. The detector was placed at a depth of about 1.5X0, followed by an electromagnetic and hadronic calorimeter, and exposed to positron, positively charged pion and positive muon beams with energies in the range of 5–227 GeV. Multianode phototubes, HAMAMATSU R5900-M16, were used for the photon readout. The efficiency for detecting two minimum ionizing particles with noise occupancy of <1% was 90–100% for gains of (1–4)×105. It was also found that by requiring an appropriately large signal in the preshower detector, the rate of charged pions depositing a large fraction of energy in the electromagnetic calorimeter could be reduced by a factor of 1.4–2.0 (1.4–2.8) while keeping 95% (90%) efficiency for positrons.

Search for a Technicolor ωT Particle in Events with a Photon and a b-Quark Jet at Fermilab

If the technicolor {omega}{sub T} particle exists, a likely decay mode is {omega}{sub T}{r_arrow}{gamma}{pi}{sub T} , followed by {pi}{sub T}{r_arrow}b{bar b} , yielding the signature {gamma}b{bar b} . We have searched 85 pb{sup {minus}1} of data collected by the CDF experiment at the Fermilab Tevatron for events with a photon and two jets, where one of the jets must contain a secondary vertex implying the presence of a b quark. We find no excess of events above standard model expectations. We express the result as an exclusion region in the M{sub {omega}{sub T}}-M{sub {pi}{sub T}} mass plane. {copyright} {ital 1999} {ital The American Physical Society }