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.
We report on measurements of the ϒ(1S), ϒ(2S), and ϒ(3S) differential, (d2σdPtdy)y=0, and integrated cross sections in pp¯ collisions at s=1.8 TeV using a sample of 16.6 ± 0.6 pb−1 collected by the Collider Detector at Fermilab. The three resonances were reconstructed through the decay ϒ→μ+μ−. Comparison is made to a leading order QCD prediction.
We have measured the differential cross section for the inclusive production of psi(2S) mesons decaying to mu^{+} mu^{-1} that were produced in prompt or B-decay processes from ppbar collisions at 1.96 TeV. These measurements have been made using a data set from an integrated luminosity of 1.1 fb^{-1} collected by the CDF II detector at Fermilab. For events with transverse momentum p_{T} (psi(2S)) > 2 GeV/c and rapidity |y(psi(2S))| < 0.6 we measure the integrated inclusive cross section sigma(ppbar -> psi(2S)X) Br(psi(2S) -> mu^{+} mu^{-}) to be 3.29 +- 0.04(stat.) +- 0.32(syst.) nb.
We study charged particle production in proton-antiproton collisions at 300 GeV, 900 GeV, and 1.96 TeV. We use the direction of the charged particle with the largest transverse momentum in each event to define three regions of eta-phi space; toward, away, and transverse. The average number and the average scalar pT sum of charged particles in the transverse region are sensitive to the modeling of the underlying event. The transverse region is divided into a MAX and MIN transverse region, which helps separate the hard component (initial and final-state radiation) from the beam-beam remnant and multiple parton interaction components of the scattering. The center-of-mass energy dependence of the various components of the event are studied in detail. The data presented here can be used to constrain and improve QCD Monte Carlo models, resulting in more precise predictions at the LHC energies of 13 and 14 TeV.
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.
A strong signal for double parton (DP) scattering is observed in a 16pb−1 sample of p¯p→γ/π0+3jets+X data from the CDF experiment at the Fermilab Tevatron. In DP events, two separate hard scatterings take place in a single p¯p collision. We isolate a large sample of data (∼14000events) of which 53% are found to be DP. The process-independent parameter of double parton scattering, σeff, is obtained without reference to theoretical calculations by comparing observed DP events to events with hard scatterings in separate p¯p collisions. The result σeff=(14.5±1.7−2.3+1.7)mb represents a significant improvement over previous measurements, and is used to constrain simple models of parton spatial density. The Feynman x dependence of σeff is investigated and none is apparent. Further, no evidence is found for kinematic correlations between the two scatterings in DP events.
We present a study of events with Z bosons and hadronic jets produced in $\overline{p}p$ collisions at a center-of-mass energy of 1.8 TeV. The data consist of 6708 $Z \rightarrow e~+e~-$ decays from 106 pb$~{-1}$ of integrated luminosity collected using the CDF detector at the Tevatron Collider. The Z $+ \ge n$ jet cross sections and jet production properties have been measured for n = 1 to 4. The data compare well to predictions of leading order QCD matrix element calculations with added gluon radiation and simulated parton 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 jet differential cross section has been measured for jet transverse energies, $E_T$, from 15 to 440 GeV, in the pseudorapidity region 0.1$\leq | \eta| \leq $0.7. The results are based on 19.5 pb$~{-1}$ of data collected by the CDF collaboration at the Fermilab Tevatron collider. The data are compared with QCD predictions for various sets of parton distribution functions. The cross section for jets with $E_T>200$\ GeV is significantly higher than current predictions based on O($\alpha_s~3$) perturbative QCD calculations. Various possible explanations for the high-$E_T$\ excess are discussed.