We present a measurement of the isolated direct photon cross section in p-pbar collisions at sqrt(s) = 1.8 TeV and |eta| < 0.9 using data collected between 1994 and 1995 by the Collider Detector at Fermilab (CDF). The measurement is based on events where the photon converts into an electron-positron pair in the material of the inner detector, resulting in a two-track event signature. To remove pi0 -> gamma gamma and eta -> gamma gamma events we use a new background subtraction technique which takes advantage of the tracking information available in a photon conversion event. We find that the shape of the cross section as a function of pT is poorly described by next-to-leading-order QCD predictions, but agrees with previous CDF measurements.

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 the branching ratios of the decays B+→χc10(1P)K+ and B+→J/ψK+π+π−, where χc10(1P)→J/ψγ and J/ψ→μ+μ− in pp¯ collisions at s=1.8TeV. Using a data sample from an integrated luminosity of 110pb−1 collected by the Collider Detector at Fermilab we measure the branching ratios to be BR(B+→χc10(1P)K+)=15.5±5.4(stat)±1.5(syst)±1.3(br)×10−4 and BR(B+→J/ψK+π+π−)=6.9±1.8(stat)±1.1(syst)±0.4(br)×10−4 where (br) is due to the finite precision on BR(B+→J/ψK+), BR(χc10(1P)→J/ψγ) is used to normalize the signal yield, and (syst) encompasses all other systematic uncertainties.

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.

The transverse momentum cross section of $e^+e^-$ pairs in the $Z$-boson mass region of 66-116 GeV/$c^2$ is precisely measured using Run II data corresponding to 2.1 fb$^{-1}$ of integrated luminosity recorded by the Collider Detector at Fermilab. The cross section is compared with quantum chromodynamic calculations. One is a fixed-order perturbative calculation at ${\cal O}(\alpha_s^2)$, and the other combines perturbative predictions at high transverse momentum with the gluon resummation formalism at low transverse momentum. Comparisons of the measurement with calculations show reasonable agreement. The measurement is of sufficient precision to allow refinements in the understanding of the transverse momentum distribution.

This article reports a measurement of the production cross section of prompt isolated photon pairs in proton-antiproton collisions at \sqrt{s} = 1.96 TeV using the CDF II detector at the Fermilab Tevatron collider. The data correspond to an integrated luminosity of 5.36/fb. The cross section is presented as a function of kinematic variables sensitive to the reaction mechanisms. The results are compared with three perturbative QCD calculations: (1) a leading order parton shower Monte Carlo, (2) a fixed next-to-leading order calculation and (3) a next-to-leading order/next-to-next-to-leading-log resummed calculation. The comparisons show that, within their known limitations, all calculations predict the main features of the data, but no calculation adequately describes all aspects of the data.

We report measurements of the inclusive transverse momentum pT distribution of centrally produced kshort, kstar(892), and phi(1020) mesons up to pT = 10 GeV/c in minimum-bias events, and kshort and lambda particles up to pT = 20 GeV/c in jets with transverse energy between 25 GeV and 160 GeV in pbar p collisions. The data were taken with the CDF II detector at the Fermilab Tevatron at sqrt(s) = 1.96 TeV. We find that as pT increases, the pT slopes of the three mesons (kshort, kstar, and phi) are similar, and the ratio of lambda to kshort as a function of pT in minimum-bias events becomes similar to the fairly constant ratio in jets at pT ~ 5 GeV/c. This suggests that the particles with pT >~ 5 GeV/c in minimum-bias events are from soft jets, and that the pT slope of particles in jets is insensitive to light quark flavor (u, d, or s) and to the number of valence quarks. We also find that for pT <~ 4 GeV relatively more lambda baryons are produced in minimum-bias events than in jets.

We report a set of measurements of inclusive invariant transverse momentum differential cross sections of lambda, cascade and omega hyperons reconstructed in the central region with pseudorapidity within 1 and transverse momentum up to 10 GeV/c Events are collected with a minimum-bias trigger in ppbar collisions at a center-of-mass energy of 1.96 TeV using the CDF II detector at the Tevatron Collider. As transverse momentum increases, the slopes of the differential cross sections are similar not only to each other but also to those of mesons, which could indicate a universality of the particle production in transverse momentum The invariant differential cross sections are also presented for different charged-particle multiplicity intervals.

A measurement of the top-quark pair-production cross section in ppbar collisions at sqrt{s}=1.96 TeV using data corresponding to an integrated luminosity of 1.12/fb collected with the Collider Detector at Fermilab is presented. Decays of top-quark pairs into the final states e nu + jets and mu nu + jets are selected, and the cross section and the b-jet identification efficiency are determined using a new measurement technique which requires that the measured cross sections with exactly one and multiple identified b-quarks from the top-quark decays agree. Assuming a top-quark mass of 175 GeV/c^2, a cross section of 8.5+/-0.6(stat.)+/-0.7(syst.) pb is measured.

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.