A. Akopian

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.

Search for Gluinos and Squarks Using Like-Sign Dileptons in p overline(p) Collisions at sqrt(s) = 1.8 TeV

We present results of the first search for like-sign dilepton (ee, e\mu, \mu\mu) events associated with multijets and large missing energy using 106 pb^-1 of data in p-pbar collisions at sqrt(s)=1.8 TeV collected during 1992-95 by the CDF experiment. Finding no events that pass our selection, we examine pair-production of gluinos and squarks in a constrained framework of the Minimal Supersymmetric Standard Model. At tan_beta = 2 and \mu=-800 GeV/c^2, we set 95% confidence level limits of M(gluino)>221 GeV/c^2 for M(gluino) \simeq M(squark), and M(gluino)>168 GeV/c^2 for M(squark) \gg M(gluino), both with small variation as a function of \mu.

Observation of Top Quark Production in p-barp Collisions with the Collider Detector at Fermilab.

We establish the existence of the top quark using a 67pb{sup {minus}1} data sample of {ital p}{ovr bar}{ital p} collisions at {radical}{ital s}=1.8TeV collected with the Collider Detector at Fermilab (CDF). Employing techniques similar to those we previously published, we observe a signal consistent with {ital tb}{ovr bar}, but inconsistent with the background prediction by 4.8{sigma}. Additional evidence for the top quark is provided by a peak in the reconstructed mass distribution. We measure the top quark mass to be 176{plus_minus}8(stat){plus_minus}10(syst)GeV/{ital c}{sup 2}, and the {ital tt}{ovr bar} production cross section to be 6.8{sub {minus}2.4}{sup +3.6}pb.We establish the existence of the top quark using a 67 pb^-1 data sample of Pbar-P collisions at Sqrt(s) = 1.8 TeV collected with the Collider Detector at Fermilab (CDF). Employing techniques similar to those we previously published, we observe a signal consistent with t-tbar decay to WW b-bbar, but inconsistent with the background prediction by 4.8 sigma. Additional evidence for the top quark is provided by a peak in the reconstructed mass distribution. We measure the top quark mass to be 176 +/-8(stat) +/- 10(sys.) GeV/c^2, and the t-tbar production cross section to be 6.8 +3.6 -2.4 pb.

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.

Search for Neutral Supersymmetric Higgs Bosons in pp-bar Collisions at sqrt(s) = 1.8 TeV

We present the results of a search for neutral Higgs bosons produced in association with b quarks in pp-->bb(phi)-->bbb final states with 91+/-7 pb(-1) of pp collisions at sqrt[s] = 1.8 TeV recorded by the Collider Detector at Fermilab. We find no evidence of such a signal and the data are interpreted in the context of the neutral Higgs sector of the minimal supersymmetric extension of the standard model. With basic parameter choices for the supersymmetric scale and the stop-quark mixing, we derive 95% C.L. lower mass limits for neutral Higgs bosons for tan(beta) values in excess of 35.

Search for gluinos and squarks using like-sign dileptons in {ovr p}p collisions at {radical}{ovr s}= 1.8 TeV.

We present results of the first search for like-sign dilepton (ee, e\mu, \mu\mu) events associated with multijets and large missing energy using 106 pb^-1 of data in p-pbar collisions at sqrt(s)=1.8 TeV collected during 1992-95 by the CDF experiment. Finding no events that pass our selection, we examine pair-production of gluinos and squarks in a constrained framework of the Minimal Supersymmetric Standard Model. At tan_beta = 2 and \mu=-800 GeV/c^2, we set 95% confidence level limits of M(gluino)>221 GeV/c^2 for M(gluino) \simeq M(squark), and M(gluino)>168 GeV/c^2 for M(squark) \gg M(gluino), both with small variation as a function of \mu.

Measurement of the t{ovr t} production cross section in p{ovr p} collisions at {radical}{ovr s} = 1.8 TeV.

We update the measurement of the t{bar t} production cross section using the CDF detector at the Fermilab Tevatron. This measurement use t{bar t} decays to the final states e+v+jets and {mu}+v+jets. We search for b quarks from t decays via secondary-vertex identification or the identification of semileptonic decayse of the b and cascade c quarks. The background to the t{bar t} production is determined primarily through a Monte Carlo simulation. However, we calibrate the simulation and evaluate its uncertainty using several independent data samples. For a top quark mass of 175 GeV/c{sup 2}, we measure {sigma}{sub t{bar t}}=5.1{+-}1.5 pb and {sigma}{sub t{bar t}}=9.2{+-}4.3 pb using the secondary vertex and the lepton tagging algorithms, respectively. Finally, we combine these results with those from other t{bar t} decay channels and obtain {sigma}{sub t{bar t}}=6.5{sub -1.4}{sup +1.7} pb.

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 inclusive jet cross section in {ovr p}p collisions at {radical}{ovr s} {equals} 1.8 TeV.

Z

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

-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.