Search

We report on the observation of b-hadron states reconstructed using the DØ detector data at the Tevatron Collider. Measurements of the mass and relative rates of neutral excited and mesons, and the discovery of the baryon are described. [Copyright &y& Elsevier]

We present the first next-to-leading-order QCD analysis of neutrino charm production, using a sample of 6090?µ- and -induced opposite-sign dimuon events observed in the CCFR detector at the Fermilab Tevatron. We find that the nucleon strange quark content is suppressed with respect to the non-strange sea quarks by a factor ?=0.477-0.053+0.063, where the error includes statistical, systematic and QCD scale uncertainties. In contrast to previous leading order analyses, we find that the strange seax-dependence is similar to that of the non-strange sea, and that the measured charm quark mass,mc=1.70±0.19 GeV/c2, is larger and consistent with that determined in other processes. Further analysis finds that the difference inx-distributions betweenxs(x) and is small. A measurement of the Cabibbo-Kobayashi-Maskawa matrix element |Vcd|=0.232-0.020+0.018 is also presented.

Abstract: We report on a search forv $$\bar v_\mu $$ -induced charged current interactions and ngr-induced interactions that produce dileptons. We derive an upper limit on the rate of wrong-sign single muon production relative to the rate ofv mgr charged current interactions to be 1.6×10–4 fory<0.5 and 3.1×10–4 fory>0.5 (90% CL). These upper limits enable us to constrain exotic sources of wrong-sign muons such as the charm component of the nucleon sea, flavor changing neutral currents and lepton number violating processes. Finally, the rate and kinematic properties of these events are compared with those of the neutrino-induced opposite-sign dimuon events.

A search for inclusive muon-neutrino (vµ) and muon-antineutrino oscillations has been performed in the Fermilab narrow band neutrino beam using two detectors running simultanously at two distances from the neutrino source. The data show no evidence for either neutrino or antineutrino oscillations and rule out oscillations ofvµ or into any other single type of neutrino for 15<Δm2<1,000 eV2/c4 and sin2(2θ)>0.02–0.40.

We report a measurement of the electroweak parameters sin2?w and ? based on the ratios of neutral current to charged current events measured in the Fermilab narrow-band neutrino beam at energies of 30–240 GeV. The data are fully corrected for radiative effects, heavy-quark production, and other effects. The best value for sin2?w obtained, sin2?w=0.239±0.011, is consistent with the most recent values fromW andZ production, as well as from other neutrino experiments.

This paper reports on measurements of the total cross section for the inclusive reaction vµ+N, as a function of incident energy. Neutrinos and antineutrinos with energy in the range 30–300 GeV were produced in the 1982 Fermilab narrow-band neutrino beamline. A total of 35 000 neutrino and 7000 antineutrino interactions were recorded in the CCFR detector located in LabE. The incident neutrino flux was determined by methods similar to those used in previous experiments. The rate of increase with energy of the total cross section (s/Ev) in the range 30 to 75 GeV was determined to be 0.659±0.005(stat)±0.039(syst)×10-38 cm2/GeV and 0.307±0.008(stat)±0.020(syst)×10-38 cm2/GeV for incident neutrinos and antineutrinos, respectively. The 5.9% systematic errors are due primarily to uncertainties in the flux intensity measurement. The energy dependence of the cross section in the regionE?=100–300 GeV was found to be linear, as determined by relative normalization techniques. A weighted average of our previous and present measurement for the total ?-N cross section yields: $$\begin{gathered} \sigma (vN) = 0.666 \pm 0.020(statistical \hfill \\ + systematic)E_v 10^{ - 38} cm^2 ; \hfill \\ \sigma (\bar vN) = 0.324 \pm 0.014(statistical \hfill \\ + systematic)E_v 10^{ - 38} cm^2 ; \hfill \\ \end{gathered} $$ .

Neutrino interactions with two muons in the final state have been studied using the Fermilab narrow band beam. A sample of 18vµ like sign dimuon events withPµ>9 GeV/c yields 6.6±4.8 events after backgroud subtraction and a prompt rate of (1.0±0.7)×10-4 per single muon event. The kinematics of these events are compared with those of the non-prompt sources. A total of 437vµ and 31 opposite sign dimuon events withPµ>4.3 GeV/c are used to measure the strange quark content of the nucleon: using a charm semileptonic branching ratio of (10.9±1.4)% extracted from measurements ine+e- collisions and neutrino emulsion data.

We have observed Cerenkov light, well below threshold, in an integrating Cerenkov counter used to determine particle composition of the secondary hadron beam, which is the source of Fermilab narrow-band neutrinos. The phenomenon can be understood in terms of diffraction effects in a finite length counter caused by radiation emitted by particles traversing the counter even when it is evacuated. At zero pressure, the light can be considered as transition radiation produced when particles enter and leave the counter. A standard Cerenkov diffraction formula describes both the normal Cerenkov radiation and the light emitted below Cerenkov threshold.

Expression of the proapoptotic protein Bax under the control of a GAL10 promoter in Saccharomyces cerevisiae resulted in galactose-inducible cell death. Immunofluorescence studies suggested that Bax is principally associated with mitochondria in yeast cells. Removal of the carboxyl-terminal transmembrane (TM) domain from Bax [creating Bax (deltaTM)] prevented targeting to mitochondrial and completely abolished cytotoxic function in yeast cells, suggesting that membrane targeting is crucial for Bax-mediated lethality. Fusing a TM domain from Mas70p, a yeast mitochondrial outer membrane protein, to Bax (deltaTM) restored targeting to mitochondria and cytotoxic function in yeast cells. Deletion of four well-conserved amino acids (IGDE) from the BH3 domain of Bax ablated its ability to homodimerize and completely abrogated lethality in yeast cells. In contrast, several Bax mutants which retained ability to homodimerize (deltaBH1, deltaBH2, and delta1-58) also retained at least partial lethal function in yeast cells. In coimmunoprecipitation experiments, expression of the wild-type Bax protein in Rat-1 fibroblasts and 293 epithelial cells induced apoptosis, whereas the Bax (deltaIGDE) mutant failed to induce apoptosis and did not associate with endogenous wild-type Bax protein. In contrast to yeast cells, Bax (deltaTM) protein retained cytotoxic function in Rat-1 and 293 cells, was targeted largely to mitochondria, and dimerized with endogenous Bax in mammalian cells. Thus, the dimerization-mediating BH3 domain and targeting to mitochondrial membranes appear to be essential for the cytotoxic function of Bax in both yeast and mammalian cells.

Nucleon structure functions obtained from neutrino and anti-neutrino scattering on iron nuclei at high energies (Ev=30 to 250 GeV) are presented. These results are compared with the results of other lepton-nucleon scattering experiments. The structure functions are used to test the validity of the Gross-Llewellyn-smith sum rule, which measures the number of valence quarks in the nucleons, and to obtain leading and second order QCD fits.

Analytical results for 50 samples of both scoured wool and dusts secured from the grease wool comprising 24 elements (mainly mineral), moisture and ash contents are reported. Grease and suint fractions from eight fleeces, tag wool from six fleeces and cortical and cuticular preparations from the top and noil fraction of two fleeces were also analyzed for these elements, except nitrogen, phosphorus, sulfur and boron. The values of moisture, ash, nitrogen, phosphorus and sulfur for the wool samples varied within rather narrow limits. However, wide variations existed between the individual fleece values for the other elements. Copper, cobalt, molybdenum, silver and zinc were found in higher concentration in the wool than in the associated dust. Cobalt was found in detectable amounts in only five fleeces, while molybdenum was detected in only nine fleeces.The results indicate the complexities of mineral metabolism of the sheep as indicated in the chemical elements of the fleece and its component parts.

Prototype superconducting quadrupoles with a 5 cm aperture and gradient of 16 kG/cm have been built and tested as candidate magnets for the final focus at SLC. The magnets are made from NbTi Tevatron style cable with 10 inner and 14 outer turns per quadrant. Quench performance and multipole data are presented. Design and data for a low current, high gradient quadrupole, similar in cross section but wound with a cable consisting of five insulated conductors are also discussed.

We measure the mass of the top quark in lepton + jets final states using the full sample of p p collision data collected by the DO experiment in Run II of the Fermilab Tevatron Collider at √s = 1.96 TeV, corresponding to 9.7 fb-1 of integrated luminosity. We use a matrix element technique that calculates the probabilities for each event to result from tt production or background. The overall jet energy scale is constrained in situ by the mass of the W boson. We measure mt = 174.98 ± 0.76 GeV. This constitutes the most precise single measurement of the top-quark mass. [ABSTRACT FROM AUTHOR]