M. W. Bailey

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.

The CDF Plug Upgrade Electromagnetic Calorimeter: Test Beam Results

Abstract The CDF Plug Upgrade calorimeter, which fully exploits the tile–fiber technique, was tested at the Fermilab meson beamline. The calorimeter was exposed to positron, positively charged pion and positive muon beams with energies in the range of 5– 230 GeV . The energy resolution of the electromagnetic calorimeter to the positron beam is consistent with the design value of 16%/ E ⊕1% , where E is the energy in units of GeV and ⊕ represents sum in quadrature. The non-linearity for positrons is studied in an energy range of 11– 181 GeV . It is important to incorporate the response of the preshower detector, the first layer of the electromagnetic calorimeter which is readout separately, into that of the calorimeter to reduce the non-linearity to 1% or less. The energy scale is about 1.46 pC / GeV with HAMAMATSU R4125 operated typically at a gain of 2.5×10 4 . The response non-uniformity over the surface of a tower of the electromagnetic calorimeter is found to be about 2% with 57 GeV positrons. Studies of several detailed detector characteristics are also presented.

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.

Cross section and heavy quark composition of γ+μ events produced in pp̄ collisions

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 ppbar collisions recorded with the Collider Detector at Fermilab. Quantum chromodynamics (QCD) predicts that these events are primarily due to Compton scattering process charm+gluon -> charm+photon, 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 prediction. 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.

Measurement of d σ/dy for high mass Drell-Yan e+e- pairs from pp̄ collisions at √s = 1.8 TeV

We report on the first measurement of the rapidity distribution dsigma/dy over nearly the entire kinematic region of rapidity for e^+e^- pairs in the Z-boson region of 66 116 GeV/c^2. The data sample consists of 108 pb^{-1} of ppbar collisions at \sqrt{s}=1.8 TeV taken by the Collider Detector at Fermilab during 1992--1995. The total cross section in the

Measurement of the two-jet differential cross section in [Formula Presented] collisions at [Formula Presented] GeV

Z

The SVX II silicon vertex detector upgrade at CDF

-boson region is measured to be 252 +- 11 pb. The measured total cross section and d\sigma/dy are compared with quantum chromodynamics calculations in leading and higher orders.

MEASUREMENT OF W-PHOTON COUPLINGS IN P-P COLLISIONS AT S = 1.8 TEV

A measurement is presented of the two-jet differential cross section d{sup 3}{sigma}/dE{sub T}d{eta}{sub 1}d{eta}{sub 2} at center of mass energy {radical}s=1800 GeV in p{bar p} collisions. The results are based on an integrated luminosity of 86 pb{sup {minus}1} collected during 1994 to 1995 by the CDF Collaboration at the Fermilab Tevatron collider. The differential cross section is measured as a function of the transverse energy E{sub T} of a jet in the pseudorapidity region 0.1{lt}{vert_bar}{eta}{sub 1}{vert_bar}{lt}0.7 for four different pseudorapidity bins of a second jet restricted to 0.1{lt}{vert_bar}{eta}{sub 2}{vert_bar}{lt}3.0. The results are compared with next-to-leading order QCD calculations determined using the CTEQ4 and MRST sets of parton distribution functions. None of the sets examined in this analysis provides a good description of the data.