8,980,779 research outputs found

    A search for the fourth SM family quarks at Tevatron

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    It is shown that the fourth standard model (SM) family quarks can be observed at the Fermilab Tevatron if their anomalous interactions with known quarks have sufficient strength.Comment: 7 pages, 2 tables, 4 figure

    Exotic Baryons and Monopole Excitations in a Chiral Soliton Model

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    We compute the spectra of exotic pentaquarks and monopole excitations of the low--lying 1/2+{1/2}^+ and 3/2+{3/2}^+ baryons in a chiral soliton model. Once the low--lying baryon properties are fit, the other states are predicted without any more adjustable parameters. This approach naturally leads to a scenario in which the mass spectrum of the next to lowest--lying Jπ=1/2+J^\pi={1/2}^+ states is fairly well approximated by the ideal mixing pattern of the 810ˉ\mathbf{8}\oplus\bar{\mathbf{10}} representation of flavor SU(3). We compare our results to predictions obtained in other pictures for pentaquarks and speculate about the spin--parity assignment for Ξ(1690)\Xi(1690) and Ξ(1950)\Xi(1950)Comment: 16 pages, 2 figures, 6 table

    Measurement of the LT-asymmetry in \pi^0 electroproduction at the energy of the \Delta (1232) resonance

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    The reaction p(e,e'p)pi^0 has been studied at Q^2=0.2 (GeV/c)^2 in the region of W=1232 MeV. From measurements left and right of q, cross section asymmetries \rho_LT have been obtained in forward kinematics \rho_LT(\theta_\pi^0=20deg) = (-11.68 +/- 2.36_stat +/- 2.36_sys)$ and backward kinematics \rho_LT(\theta_\pi^0=160deg) =(12.18 +/- 0.27_stat +/- 0.82_sys). Multipole ratios \Re(S_1+^* M_1+)/|M_1+|^2 and \Re(S_0+^* M_1+)/|M_1+|^2 were determined in the framework of the MAID2003 model. The results are in agreement with older data. The unusally strong negative \Re(S_0+^* M_1+)/|M_1+|^2 required to bring also the result of Kalleicher et al. in accordance with the rest of the data is almost excluded.Comment: 7 pages, 7 figures, 4 tables. Changed content. Accepted for publication in EPJ

    A Covariant Path Amplitude Description of Flavour Oscillations: The Gribov-Pontecorvo Phase for Neutrino Vacuum Propagation is Right

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    An extended study is performed of geometrical and kinematical assumptions used in calculations of the neutrino oscillation phase. The almost universally employed `equal velocity' assumption, in which all neutrino mass eigenstates are produced at the same time, is shown to underestimate, by a factor of two, the neutrino propagation contribution to the phase. Taking properly into account, in a covariant path amplitude calculation, the incoherent nature of neutrino production as predicted by the Standard Model, results in an important source propagator contribution to the phase. It is argued that the commonly discussed Gaussian `wave packets' have no basis within quantum mechanics and are the result of a confused amalgam of quantum and classical wave concepts.Comment: 39 pages, 1 table, 1 figure. Subject matter similar to hep-ph/0110064, hep-ph/0110066. More pedagogical presentation addressing referee criticism of earlier paper

    Spatially Dependent Quantum Interference Effects in the Detection Probability of Charged Leptons Produced in Neutrino Interactions or Weak Decay Processes

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    Feynman's path amplitude formulation of quantum mechanics is used to analyse the production of charged leptons from charged current weak interaction processes. For neutrino induced reactions the interference effects predicted are usually called `neutrino oscillations'. Similar effects in the detection of muons from pion decay are here termed `muon oscillations'. Processes considered include pion decay (at rest and in flight), and muon decay and nuclear β\beta-decay at rest. In all cases studied, a neutrino oscillation phase different from the conventionally used one is found. A concise critical review is made of previous treatments of the quantum mechanics of neutrino and muon oscillations.Comment: 45 pages, 1 table, 3 figures. Supersedes hep-ph/0110064. Consistent use of MRS matrix to describe charged lepton-neutrino couplings. Unphysical `lepton flavour eigenstates' removed from the formalis

    Creating Ioffe-Pritchard micro-traps from permanent magnetic film with in-plane magnetization

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    We present designs for Ioffe-Pritchard type magnetic traps using planar patterns of hard magnetic material. Two samples with different pattern designs were produced by spark erosion of 40 μ\mum thick FePt foil. The pattern on the first sample yields calculated axial and radial trap frequencies of 51 Hz and 6.8 kHz, respectively. For the second sample the calculated frequencies are 34 Hz and 11 kHz. The structures were used successfully as a magneto-optical trap for 87^{87}Rb and loaded as a magnetic trap. A third design, based on lithographically patterned 250 nm thick FePt film on a Si substrate, yields an array of 19 traps with calculated axial and radial trap frequencies of 1.5 kHz and 110 kHz, respectively.Comment: 8 pages, 5 figures Revised and accepted for EPJD, improved picture

    Sea quark polarization and semi-inclusive DIS data

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    We investigate the potential impact of forthcoming Jefferson Lab semi-inclusive polarized deep inelastic scattering proton measurements in the determination of the sea quark polarization in the nucleon by means of a next to leading order global QCD analysis. Specifically, we estimate the resulting improvement in the constraints on polarized parton densities for the different flavors, which is found to be significant for up and strange quarks, and the correlation between remaining uncertainty ranges for each of the parton species.Comment: 7 pages, 4 figures. Version to be published in the European Physical Journal

    Near-threshold production of omega mesons in the pn -> d omega reaction

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    The first measurement of the p n -> d omega total cross section has been achieved at mean excess energies of Q = 28 and 57 MeV by using a deuterium cluster-jet target. The momentum of the fast deuteron was measured in the ANKE spectrometer at COSY-Juelich and that of the slow "spectator" proton p(sp) from the p d -> p(sp) d omega reaction in a silicon telescope placed close to the target. The cross sections lie above those measured for p p -> p p omega but seem to be below theoretical predictions.Comment: 7 pages, 8 figures; second approach to describe the background has been added; results changed insignificantly, EPJ in pres

    Circular 58

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    A comparative yield trial with 44 named varieties and numbered selections of potatoes was conducted at the University of Alaska-Fairbanks, Agricultural and Forestry Experiment Station’s (AFES) Palmer Research Center during the 1986 growing season. This yield trial is the continuation of a potato variety testing program initiated in 1982. The trial again was conducted at the Matanuska Research Farm, located on Trunk Road near Palmer. Nonirrigated trials have been conducted each year beginning in 1982, but irrigated trials were not initiated until 1985. Results of previous trials are recorded in Circulars 49 and 54, available at the Agricultural and Forestry Experiment Station offices in Fairbanks and Palmer. As in past years, varieties with long production histories in Alaska (Alaska 114, Bakeking, Green Mountain, Kennebec, Superior) are included and serve as a comparative base for newly developed varieties or older varieties that in the past have escaped testing at this location. Varieties that compare favorably with the above listed standards may warrant some consideration by commercial growers. In continuance of a program that was initiated in 1985, abbreviated versions of the AFES potato yield trial were conducted at locations in various parts of the state. These off-station trials again were made possible by the willingness of cooperators to plant, tend and harvest the crop. The seven off-station sites include several where comparative testing of potato varieties has not been reported previously.Introduction -- Matanuska Farm Yield Trials: Cultural Practices - Environmental Conditions, Results, Discussion -- Trials at Other Locations in Alaska: General Procedures, Specific Site Information: Ambler, Copper Center, Delta Junction, Fairbanks, Kake, Kodiak, Noorvi
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