We present a study of events with W bosons and hadronic jets produced in pbar p collisions at a center of mass energy of 1.8 TeV. The data consist of 51400 W^+/- -> e^+/- nu decay candidates from 108 pb^-1 of integrated luminosity collected with the CDF detector at the Tevatron Collider. The cross sections and jet production properties have been measured for W + \geq 1 to \geq 4 jet events. The data are compared to predictions of leading order QCD matrix element calculations with added gluon radiation and simulated fragmentation.

We report on measurements of the ϒ(1S), ϒ(2S), and ϒ(3S) differential cross sections (d2σ/dpTdy)|y|<0.4, as well as on the ϒ(1S) polarization in pp¯ collisions at s=1.8TeV using a sample of 77±3pb−1 collected by the collider detector at Fermilab. The three resonances were reconstructed through the decay ϒ→μ+μ−. The measured angular distribution of the muons in the ϒ(1S) rest frame is consistent with unpolarized meson production.

The growth and development of “charged particle jets” produced in proton-antiproton collisions at 1.8 TeV  are studied over a transverse momentum range from 0.5 GeV/c to 50 GeV/c. 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 η−φ 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 2-to-2 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.

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(pT>10GeV/c,2.1<|η|<2.6)+X]/dη=192±9(stat)±29(syst)pb. The results are based on 74.1±5.2pb−1 of data collected by the CDF Collaboration at the Fermilab Tevatron Collider. The measurements extend earlier measurements of the D0 Collaboration to higher pTJ/ψ. In the kinematic range where the experiments partially overlap, these data are in good agreement with previous measurements.

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.

We report on a measurement of the mean charged-particle multiplicity of jets in dijet events with dijet masses in the range 80–630GeV/c2, produced at the Tevatron in pp¯ collisions with s=1.8TeV and recorded by the Collider Detector at Fermilab. The data are fit to perturbative-QCD calculations carried out in the framework of the modified leading log approximation and the hypothesis of local parton-hadron duality. The fit yields values for two parameters in that framework: the ratio of parton multiplicities in gluon and quark jets, $r≡N_{partons}^{g−jet} / N_{partons}^{q−jet} = 1.7 \pm 0.3$, and the ratio of the number of charged hadrons to the number of partons in a jet, $K_{LPHD}^{charged} ≡ N_{hadrons}^{charged} / N_{partons} = 0.57 \pm 0.11$.

We present the results of a search for neutral Higgs bosons produced in association with $b$ quarks in $p\bar{p}\to b\bar{b} \phi\to b\bar{b}b\bar{b}$ final states with $91 \pm 7$ pb$^{-1}$ of $p\bar{p}$ 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 is 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 $\tb$ values in excess of 35.

We have measured the ratio of prompt production rates of the charmonium states χc1 and χc2 in 110pb−1 of pp¯ collisions at s=1.8TeV. The photon from their decay into J/ψγ is reconstructed through conversion into e+e− pairs. The energy resolution this technique provides makes the resolution of the two states possible. We find the ratio of production cross sections σχc2σχc1=0.96±0.27(stat)±0.11(syst) for events with pT(J/ψ)>4.0GeV/c, |η(J/ψ)|<0.6, and pT(γ)>1.0GeV/c.

We present a search for first generation leptoquark with 110pb^1 of data collected with the CDF detector. We set 95% C.L. cross section limits as a function of the leptoquark mass.

We present results from the measurement of the inclusive jet cross section for jet transverse energies from 40 to 465 GeV in the pseudo-rapidity range $0.1<|\eta|<0.7$. The results are based on 87 $pb^{-1}$ of data collected by the CDF collaboration at the Fermilab Tevatron Collider. The data are consistent with previously published results. The data are also consistent with QCD predictions given the flexibility allowed from current knowledge of the proton parton distributions. We develop a new procedure for ranking the agreement of the parton distributions with data and find that the data are best described by QCD predictions using the parton distribution functions which have a large gluon contribution at high $E_T$ (CTEQ4HJ).

We present a study of pp¯ collisions at s=1800 and 630 GeV collected using a minimum bias trigger by the CDF experiment in which the data set is divided into two classes corresponding to “soft” and “hard” interactions. For each subsample, the analysis includes measurements of the multiplicity, transverse momentum (pT) spectrum, and the average pT and event-by-event pT dispersion as a function of multiplicity. A comparison of results shows distinct differences in the behavior of the two samples as a function of the center of mass (c.m.) energy. We find evidence that the properties of the soft sample are invariant as a function of c.m. energy.

We have searched for the rare decay W±→π±+γ in 83 pb−1 of data taken in proton-antiproton collisions at s=1.8 TeV with the Collider Detector at Fermilab. We find three events in the signal region and estimate the background to be 5.2±1.5 events. We set a 95% confidence level upper limit of 7×10−4 on the ratio of partial widths, Γ(W±→π±+γ)/Γ(W±→e±+ν).

We present a study of the production of K_s^0 and Lambda^0 in inelastic pbar-p collisions at sqrt(s)= 1800 and 630 GeV using data collected by the CDF experiment at the Fermilab Tevatron. Analyses of K_s^0 and Lambda^0 multiplicity and transverse momentum distributions, as well as of the dependencies of the average number and <p_T> of K_s^0 and Lambda^0 on charged particle multiplicity are reported. Systematic comparisons are performed for the full sample of inelastic collisions, and for the low and high momentum transfer subsamples, at the two energies. The p_T distributions extend above 8 GeV/c, showing a <p_T> higher than previous measurements. The dependence of the mean K_s^0(Lambda^0) p_T on the charged particle multiplicity for the three samples shows a behavior analogous to that of charged primary tracks.

We report on measurements of differential cross sections d sigma/d p_t for prompt charm meson production in p anti-p collisions at s**(1/2) = 1.96 TeV using 5.8 +/- 0.3 pb-1 of data from the CDF II detector at the Fermilab Tevatron. The data are collected with a new trigger that is sensitive to the long lifetime of hadrons containing heavy flavor. The charm meson cross sections are measured in the central rapidity region |y| \leq 1 in four fully reconstructed decay modes: D0 --> K- pi+, D*+ -> D0 pi+, D+ --> K- pi+ pi+, D+_s--> phi pi+, and their charge conjugates. The measured cross sections are compared to theoretical calculations.

We have measured the polarization of J/Psi and Psi(2S) mesons produced in p\bar{p} collisions at \sqrt{s} = 1.8 TeV, using data collected at CDF during 1992-95. The polarization of promptly produced J/Psi [Psi(2S)] mesons is isolated from those produced in B-hadron decay, and measured over the kinematic range 4[5.5] < P_T < 20 GeV/c and |y| < 0.6. For P_T \gessim 12 GeV/c we do not observe significant polarization in the prompt component.

We present a study of events with W bosons and hadronic jets produced in p¯p collisions at a center of mass energy of 1.8 TeV. The data consist of 51400 W→eν decay candidates from 108 pb−1 of integrated luminosity collected using the CDF detector at the Fermilab Tevatron collider. Cross sections and jet production properties have been measured for W+>~1 to >~4 jet events. The data compare well to predictions of leading-order QCD matrix element calculations with added gluon radiation and simulated parton fragmentation.

The Standard Model predictions for $W\gamma$ and $Z\gamma$ production are tested using an integrated luminosity of 200 pb$^{-1}$ of \ppbar collision data collected at the Collider Detector at Fermilab. The cross sections are measured selecting leptonic decays of the $W$ and $Z$ bosons, and photons with transverse energy $E_T>7$ GeV that are well separated from leptons. The production cross sections and kinematic distributions for the $W\gamma$ and $Z\gamma$ are compared to SM predictions.

We report on a study of jet shapes in inclusive jet production in $p \bar{p}$ collisions at $\sqrt{s} = 1.96 {\rm TeV}$ using the upgraded Collider Detector at Fermilab in Run II (CDF II) based on an integrated luminosity of $170 \rm pb^{-1}$. Measurements are carried out on jets with rapidity $0.1 < |Y^{\rm jet}| < 0.7$ and transverse momentum 37 GeV/c $< P_T^{\rm jet} < 380$ GeV/c. The jets have been corrected to the hadron level. The measured jet shapes are compared to leading-order QCD parton-shower Monte Carlo predictions as implemented in the PYTHIA and HERWIG programs. PYTHIA, tuned to describe the underlying event as measured in CDF Run I, provides a better description of the measured jet shapes than does PYTHIA or HERWIG with their default parameters.

A measurement is presented of the two-jet differential cross section, d^3\sigma/dE_T d\eta_1 d\eta_2, at center of mass energy sqrt{s} = 1800 GeV in proton-antiproton collisions. The results are based on an integrated luminosity of 86 pb^-1 collected during 1994-1995 by the CDF collaboration at the Fermilab Tevatron collider. The differential cross section is measured as a function of the transverse energy, E_T, of a jet in the pseudorapidity region 0.1 &lt; |eta_1| &lt; 0.7 for four different pseudorapidity bins of a second jet restricted to 0.1 &lt; |\eta_2| &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.

We present a measurement of the t-tbar cross section in p-pbar collisions at sqrt(s)=1.8 TeV using an integrated luminosity of 109 pb-1 collected with the Collider Detector at Fermilab. The measurement uses t-tbar decays into final states which contain one or two high transverse momentum leptons and multiple jets, and final states which contain only jets. Using acceptances appropriate for a top quark mass of 175 GeV/c^2, we find sigma(t-tbar)=7.6 (+1.8 -1.5) pb .

We have used 87 pb^-1 of data collected with the Collider Detector at Fermilab to search for new particles decaying to b bbar. We present model-independent upper limits on the cross section for narrow resonances which excludes the color-octet technirho in the mass interval 350 < M < 440 GeV/c^2. In addition, we exclude topgluons, predicted in models of topcolor-assisted technicolor, of width Gamma = 0.3 M in the mass range 280 < M < 670 GeV/c^2, of width Gamma = 0.5 M in the mass range 340 < M < 640 GeV/c^2, and of width Gamma = 0.7 M in the mass range 375 < M < 560 GeV/c^2.

We update the measurement of the top production cross section using the CDF detector at the Fermilab Tevatron. This measurement uses $t\bar{t}$ decays to the final states $e+\nu$+jets and $\mu+\nu$+jets. We search for $b$ quarks from $t$ decays via secondary-vertex identification or the identification of semileptonic decays 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 mass of 175 $GeV/c^2$, we measure $\sigma_{t\bar{t}}=5.1 \pm 1.5$ pb and $\sigma_{t\bar{t}}=9.2 \pm 4.3$ 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 $\sigma_{t\bar{t}} = 6.5^{+1.7}_{-1.4}$ pb.

We report a measurement of the rate of prompt diphoton production in $p\bar{p}$ collisions at $\sqrt{s}=1.96 ~\hbox{TeV}$ using a data sample of 207 pb$^{-1}$ collected with the upgraded Collider Detector at Fermilab (CDF II). The background from non-prompt sources is determined using a statistical method based on differences in the electromagnetic showers. The cross section is measured as a function of the diphoton mass, the transverse momentum of the diphoton system, and the azimuthal angle between the two photons and is found to be consistent with perturbative QCD predictions.

We have searched for exclusive 2-photon production in proton-antiproton collisions at sqrt{s} = 1.96 TeV, using 532/pb of integrated luminosity taken by the Run II Collider Detector at Fermilab. The event signature requires two electromagnetic showers, each with transverse energy E_T > 5 GeV and pseudorapidity |eta|&lt;1.0, with no other particles detected in the event. Three candidate events are observed. We discuss the consistency of the three events with gamma-gamma, pi0-pi0, or eta-eta production. The probability that other processes fluctuate to 3 events or more is 1.7x10^-4. An upper limit on the cross section of p+pbar --> p+gamma-gamma+pbar is set at 410 fb with 95% confidence level.

We present the first observation of exclusive $e^+e^-$ production in hadron-hadron collisions, using $p\bar{p}$ collision data at \mbox{$\sqrt{s}=1.96$ TeV} taken by the Run II Collider Detector at Fermilab, and corresponding to an integrated luminosity of \mbox{532 pb$^{-1}$}. We require the absence of any particle signatures in the detector except for an electron and a positron candidate, each with transverse energy {$E_T>5$ GeV} and pseudorapidity {$|\eta|<2$}. With these criteria, 16 events are observed compared to a background expectation of {$1.9\pm0.3$} events. These events are consistent in cross section and properties with the QED process \mbox{$p\bar{p} \to p + e^+e^- + \bar{p}$} through two-photon exchange. The measured cross section is \mbox{$1.6^{+0.5}_{-0.3}\mathrm{(stat)}\pm0.3\mathrm{(syst)}$ pb}. This agrees with the theoretical prediction of {$1.71 \pm 0.01$ pb}.