10,581,671 research outputs found

    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

    Quantifying bid-ask spreads in the Chinese stock market using limit-order book data: Intraday pattern, probability distribution, long memory, and multifractal nature

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    The statistical properties of the bid-ask spread of a frequently traded Chinese stock listed on the Shenzhen Stock Exchange are investigated using the limit-order book data. Three different definitions of spread are considered based on the time right before transactions, the time whenever the highest buying price or the lowest selling price changes, and a fixed time interval. The results are qualitatively similar no matter linear prices or logarithmic prices are used. The average spread exhibits evident intraday patterns consisting of a big L-shape in morning transactions and a small L-shape in the afternoon. The distributions of the spread with different definitions decay as power laws. The tail exponents of spreads at transaction level are well within the interval (2,3)(2,3) and that of average spreads are well in line with the inverse cubic law for different time intervals. Based on the detrended fluctuation analysis, we found the evidence of long memory in the bid-ask spread time series for all three definitions, even after the removal of the intraday pattern. Using the classical box-counting approach for multifractal analysis, we show that the time series of bid-ask spread does not possess multifractal nature.Comment: 8 EPJ pages including 7 eps figure

    The high-energy hadron spin-flip amplitude at small momentum transfer and new AN data from RHIC

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    In the case of elastic high-energy hadron-hadron scattering, the impact of the large-distance contributions on the behaviour of the slopes of the spin-non-flip and of the spin-flip amplitudes is analysed. It is shown that the long tail of the hadronic potential in impact parameter space leads to a value of the slope of the reduced spin-flip amplitude larger than that of the spin-non-flip amplitude. This effect is taken into account in the calculation of the analysing power in proton-nucleus reactions at high energies. It is shown that the preliminary measurement of AN obtained by the E950 Collaboration indeed favour a spin-flip-amplitude with a large slope. Predictions for AN at pL = 250 GeV/c are given.Comment: 16 pages, 5 figures, a few typos fixed in v.

    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

    Direct Fragmentation of Quarkonia Including Fermi Motion Using Light-cone Wave Function

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    We investigate the effect of Fermi motion on the direct fragmentation of the J/ψJ/\psi and Υ\Upsilon states employing a light-cone wave function. Consistent with such a wave function we set up the kinematics of a heavy quark fragmenting into a quarkonia such that the Fermi motion of the constituents split into longitudinal as well as transverse direction and thus calculate the fragmentation functions for these states. In the framework of our investigation, we estimate that the fragmentation probabilities of J/ψJ/\psi and Υ\Upsilon may increase at least up to 14 percent when including this degree of freedom.Comment: 7 pages 5 figures Appeared in EPJC; Fig 1 and Appendix revise

    Signatures of Chiral Dynamics in Low Energy Compton Scattering off the Nucleon

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    We present a projector formalism which allows to define dynamical polarizabilities of the nucleon from a multipole expansion of the nucleon Compton amplitudes. We give predictions for the energy dependence of these dynamical polarizabilities both from dispersion theory and from leading-one-loop chiral effective field theory. Based on the good agreement between the two theoretical frameworks, we conclude that the energy dependence of the dynamical polarizabilities is dominated by chiral dynamics, except in those multipole channels where the first nucleon resonance Delta(1232) can be excited. Both the dispersion theory framework and a chiral effective field theory with explicit Delta(1232) degrees of freedom lead to a very good description of the available low energy proton Compton data. We discuss the sensitivity of the proton Compton cross section to dynamical polarizabilities of different multipole content and present a fit of the static electric and magnetic dipole polarizabilities from low-energy Compton data up to omega=170 MeV, finding alpha_E=(11.04+-1.36)*10^(-4) fm^3, beta_M =(2.76-+1.36)*10^(-4) fm^3.Comment: 43 pages, 13 figure

    63rd Commencement Address

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    Judge Wald offers advice to graduates, including: But the most valuable legacy college can leave you Is an appetite and appreciation of language. Clarity, lucidity, precision with words is the most elusive of talents. Words inform, inspire, mislead and sometimes destroy. They are the most essential tool of humanity. Words plan, build, preserve, and often demolish civilizations, industries, empires, governments, and relationships. If you carry one lesson from college to life, let it be the knowledge that what you say is the expression of what you mean, what you intend to provoke in others, what you want to realize

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    No-core shell model for 48-Ca, 48-Sc and 48-Ti

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    We report the first no-core shell model results for 48Ca^{48}Ca, 48Sc^{48}Sc and 48Ti^{48}Ti with derived and modified two-body Hamiltonians. We use an oscillator basis with a limited Ω\hbar\Omega range around 45/A1/325/A2/3=10.5MeV45/A^{1/3}-25/A^{2/3} = 10.5 MeV and a limited model space up to 1Ω1\hbar\Omega. No single-particle energies are used. We find that the charge dependence of the bulk binding energy of eight A=48 nuclei is reasonably described with an effective Hamiltonian derived from the CD-Bonn interaction while there is an overall underbinding by about 0.4 MeV/nucleon. However, the resulting spectra exhibit deficiencies that are anticipated due to: (1) basis space limitations and/or the absence of effective many-body interactions; and, (2) the absence of genuine three-nucleon interactions. We then introduce additive isospin-dependent central terms plus a tensor force to our Hamiltonian and achieve accurate binding energies and reasonable spectra for all three nuclei. The resulting no-core shell model opens a path for applications to the double-beta (ββ\beta\beta) decay process.Comment: Revised content and added reference
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