12,810 research outputs found

    Quasi-Inclusive and Exclusive decays of BB to η\eta'

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    We consider the effective Hamiltonian of four quark operators in the Standard Model in the exclusive and quasi-inclusive decays of the type BK()ηB\to K^{(*)} \eta^{\prime}, BηXsB\to \eta' X_s, where XsX_s contains a single Kaon. Working in the factorization assumption we find that the four quark operators can account for the recently measured exclusive decays Bη(η)KB\to \eta^{\prime}(\eta) K and BKπB\to K \pi for appropriate choice of form factors but cannot explain the large quasi-inclusive rate.Comment: Calculation of BKπB \to K \pi added and the correct BSW form factors have been used. Latex 13 papges, 1 figur

    Scattering Theory for Quantum Hall Anyons in a Saddle Point Potential

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    We study the theory of scattering of two anyons in the presence of a quadratic saddle-point potential and a perpendicular magnetic field. The scattering problem decouples in the centre-of-mass and the relative coordinates. The scattering theory for the relative coordinate encodes the effects of anyon statistics in the two-particle scattering. This is fully characterized by two energy-dependent scattering phase shifts. We develop a method to solve this scattering problem numerically, using a generalized lowest Landau level approximation.Comment: 5 pages. Published version, with clarified presentatio

    Sample-specific and Ensemble-averaged Magnetoconductance of Individual Single-Wall Carbon Nanotubes

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    We discuss magnetotransport measurements on individual single-wall carbon nanotubes with low contact resistance, performed as a function of temperature and gate voltage. We find that the application of a magnetic field perpendicular to the tube axis results in a large magnetoconductance of the order of e^2/h at low temperature. We demonstrate that this magnetoconductance consists of a sample-specific and of an ensemble-averaged contribution, both of which decrease with increasing temperature. The observed behavior resembles very closely the behavior of more conventional multi-channel mesoscopic wires, exhibiting universal conductance fluctuations and weak localization. A theoretical analysis of our experiments will enable to reach a deeper understanding of phase-coherent one-dimensional electronic motion in SWNTs.Comment: Replaced with published version. Minor changes in tex