Search for a Fourth-Generation Quark More Massive than the Z0 Boson in ppbar Collisions at sqrt(s) = 1.8 TeV

We present the results of a search for pair production of a fourth-generation charge -1/3 quark (b') in sqrt(s)=1.8 TeV ppbar collisions using 88 pb^(-1) of data obtained with the Collider Detector at Fermilab. We assume that both quarks decay via the flavor-changing neutral current process b' -> bZ and that the b' mass is greater than m_Z + m_b. We studied the decay mode b'b'bar -> ZZ b bbar where one Z0 decays into e^+e^- or mu^+ mu^- and the other decays hadronically, giving a signature of two leptons plus jets. An upper limit on the cross section of ppbar -> b'b'bar times [BR (b' -> bZ)]^2 is established as a function of the b' mass. We exclude at 95% confidence level a b' quark with mass between 100 and 199 GeV/c^2 for BR(b' -> bZ) = 100%.Comment: 12 pages, 2 figures, submitted to Phys. Rev. Letters on 9/12/9

Measurement of the Helicity of W Bosons in Top Quark Decays

We use the transverse momentum spectrum of leptons in the decay chain t-->bW with W-->l nu to measure the helicity of the W bosons in the top quark rest frame. Our measurement uses a ttbar sample isolated in 106 +/- 4 inverse picobarns of data collected in ppbar collisions at sqrt(s)=1.8 TeV with the CDF detector at the Fermilab Tevatron. Assuming a standard V--A weak decay, we find that the fraction of W's with zero helicity in the top rest frame is F_0 = 0.91 +/- 0.37 (stat) +/- 0.13 (syst), consistent with the standard model prediction of F_0=0.70 for a top mass of 175 GeV/c**2.Comment: Submitted to PRL. 8 pages, 2 figure

Production of Y(1S) Mesons from chib Decays in pp(bar) Collisions at sqrt(s)=1.8 TeV

We have reconstructed the radiative decays $\chi_{b}(1P) \to \Upsilon(1S) \gamma$ and $\chi_{b}(2P) \to \Upsilon(1S) \gamma$ in $p \bar{p}$ collisions at $\sqrt{s} = 1.8$ TeV, and measured the fraction of $\Upsilon(1S)$ mesons that originate from these decays. For $\Upsilon(1S)$ mesons with $p^{\Upsilon}_{T}>8.0$ GeV/$c$, the fractions that come from $\chi_{b}(1P)$ and $\chi_{b}(2P)$ decays are $(27.1\pm6.9(stat)\pm4.4(sys))$ and $(10.5\pm4.4(stat)\pm1.4(sys))$, respectively. We have derived the fraction of directly produced $\Upsilon(1S)$ mesons to be $(50.9\pm8.2(stat)\pm9.0(sys))$.Comment: 13 Pages, 2 figure

Measurement of the B0 anti-B0 oscillation frequency using l- D*+ pairs and lepton flavor tags

The oscillation frequency Delta-md of B0 anti-B0 mixing is measured using the partially reconstructed semileptonic decay anti-B0 -> l- nubar D*+ X. The data sample was collected with the CDF detector at the Fermilab Tevatron collider during 1992 - 1995 by triggering on the existence of two lepton candidates in an event, and corresponds to about 110 pb-1 of pbar p collisions at sqrt(s) = 1.8 TeV. We estimate the proper decay time of the anti-B0 meson from the measured decay length and reconstructed momentum of the l- D*+ system. The charge of the lepton in the final state identifies the flavor of the anti-B0 meson at its decay. The second lepton in the event is used to infer the flavor of the anti-B0 meson at production. We measure the oscillation frequency to be Delta-md = 0.516 +/- 0.099 +0.029 -0.035 ps-1, where the first uncertainty is statistical and the second is systematic.Comment: 30 pages, 7 figures. Submitted to Physical Review

Measurement of the Associated γ+μ±\gamma + \mu^\pm Production Cross Section in ppˉp \bar p Collisions at s=1.8\sqrt{s} = 1.8 TeV

We present the first measurement of associated direct photon + muon production in hadronic collisions, from a sample of 1.8 TeV $p \bar p$ collisions recorded with the Collider Detector at Fermilab. Quantum chromodynamics (QCD) predicts that these events are primarily from the Compton scattering process $cg \to c\gamma$, with the final state charm quark producing a muon. Hence this measurement is sensitive to the charm quark content of the proton. The measured cross section of $29\pm 9 pb^{-1}$ is compared to a leading-order QCD parton shower model as well as a next-to-leading-order QCD calculation.Comment: 12 pages, 4 figures Added more detailed description of muon background estimat

Measurement of b Quark Fragmentation Fractions in p-pbar Collisions at sqrt(s)=1.8 TeV

We have studied the production of B hadrons in 1.8-TeV p-pbar collisions. We present measurements of the fragmentation fractions, f_u, f_d, f_s and f_baryon, of produced b quarks that yield B^+, B^0, B^0_s and Lambda_b hadrons. Reconstruction of several electron-charm final states yields f_s/(f_u+f_d)=0.213+/-0.068 and f_baryon/(f_u+f_d)=0.118+/-0.042, assuming f_u=f_d. If all B hadrons produced in p-pbar collisions cascade to one of these four hadrons, we determine f_u=f_d=0.375+/-0.023, f_s=0.160+/-0.044 and f_baryon=0.090+/-0.029. If we do not assume f_u=f_d, we find f_d/f_u=0.84+/-0.16.Comment: 16 pages, 1 figure. Submitted to Physical Review Letter

Search for the Flavor-Changing Neutral Current Decays B^+ -> mu^+ mu^- K^+ and B^0 -> mu^+ mu^-K^{*0}

We report on a search for the flavor-changing neutral current decays B^+ -> mu^+ mu^- K^+ and B^0 -> mu^+ mu^- K^{*0} using 88 pb^{-1} of data from p-pbar collisions at \sqrt{s}=1.8 TeV, collected with the Collider Detector at Fermilab. Finding no evidence for these decays, we set upper limits on the branching fractions B(B^+ -> mu^+ mu^- K^+) mu^+ mu^-K^{*0}) < 4.0x10^{-6} at the 90% confidence level.Comment: 11 pages, 2 figures, submitted to Phys.Rev.Let

The Transverse Momentum and Total Cross Section of E+ E- Pairs in the Z-Boson Region from P Anti-P Collisions at s**(1/2) = 1.8-Tev

The transverse momentum and total cross section of e^+e^- pairs in the Z-boson region of 66<M_{ee}<116 GeV$/c^2$ from $p\bar{p}$ collisions at $\sqrt{s}=1.8$ TeV are measured using 110 pb^{-1} of collisions taken by the Collider Detector at Fermilab during 1992-1995. The total cross section is measured to be $248 \pm 11$ pb. The differential transverse momentum cross section is compared with calculations that match quantum chromodynamics perturbation theory at high transverse momentum with the gluon resummation formalism at low transverse momentum.Comment: Accepted for Publication in Phys. Rev. Letters, 7 page

Search for Scalar Top and Scalar Bottom Quarks in ppˉp\bar{p} collisions at s=1.8\sqrt{s}=1.8 TeV

We have searched for direct pair production of scalar top and scalar bottom quarks in 88 pb$^{-1}$ of $p\bar{p}$ collisions at $\sqrt{s}=1.8$ TeV with the CDF detector. We looked for events with a pair of heavy flavor jets and missing energy, consistent with scalar top quark decays to a charm quark and a neutralino, or scalar bottom quark decays to a bottom quark and a neutralino. The numbers of events that pass our selection for each process show no deviation from Standard Model expectations. We compare our results to next-to-leading order calculations for the scalar quark production cross sections to exclude regions in scalar quark-neutralino parameter space.Comment: 10 pages, 3 figures. Submitted to Physical Review Letter

Search for a W' Boson via the Decay Mode W' -> mu nu in 1.8 TeV p-pbar Collisions

We report the results of a search for a W' boson produced in p-pbar collisions at a center-of-mass energy of 1.8 TeV using a 107 pb-1 data sample recorded by the Collider Detector at Fermilab. We consider the decay channel W' -> mu nu and search for anomalous production of high transverse mass mu-nu lepton pairs. We observe no excess of events above background and set limits on the rate of W' boson production and decay relative to Standard Model W boson production and decay using a fit of the transverse mass distribution observed. If we assume Standard Model strength couplings of the W' boson to quark and lepton pairs, we exclude a W' boson with invariant mass less than 660 GeV/c**2 at 95% confidence level.Comment: 19 pages, 2 figure