4,374 research outputs found
Semi-leptonic decays heavy-light to heavy light
We present results for the QCD matrix elements involved in semi-leptonic
decays of B-mesons into pseudo scalar heavy light states. The application of
NRQCD heavy quarks allows for quark masses around the physical b-quark. We
investigate the dependence of the form factors on the external momenta and
looked at the mass dependence at zero recoil. For the first time, results for
radially excited decay products are presented.Comment: 3 pages LaTeX, 5 figures, Talk given at LATTICE99(Heavy Quarks), June
29th to July 3rd, 1999, Pisa, Ital
The unquenched Upsilon spectrum
We describe the bottomonium spectrum obtained on the UKQCD dynamical
ensembles and its comparison to quenched results. We include a determination of
alpha_s and m_b from the dynmaical results.Comment: Lattice 2000 (Heavy Quark Physics
Scaling and Further Tests of Heavy Meson Decay Constant Determinations from Nonrelativistic QCD
We present results for the B_s meson decay constant f_{B_s} from simulations
at three lattice spacings in the range a^{-1}=1.1 to 2.6 GeV using NRQCD heavy
quarks and clover light quarks in the quenched approximation. We study scaling
of this quantity and check the consistency between mesons decaying from rest
and from a state with nonzero spatial momentum. The cancellation of power law
contributions that arise in the NRQCD formulation of heavy-light currents is
discussed. On the coarsest lattice the D_s meson decay constant f_{D_s} is
calculated. Our best values for the decay constants are given by f_{B_s} =
187(4)(4)(11)(2)(7)(6) MeV and f_{D_s} = 223(6)(31)(38)(23)(9)(^{+3}_{-1}) MeV.Comment: 29 pages with 7 postscript figures, improved error analysis, version
to appear in Physical Review
Superconducting Microwave Cavity Made of Bulk MgB2
We report the successful manufacture and characterization of a microwave
resonant cylindrical cavity made of bulk MgB2 superconductor (Tc = 38.5 K),
which has been produced by the Reactive Liquid Mg Infiltration technique. The
quality factor of the cavity for the TE011 mode, resonating at 9.79 GHz, has
been measured as a function of the temperature. At T = 4.2 K, the unloaded
quality factor is 2.2x10^5; it remains of the order of 10^5 up to T ~ 30 K. We
discuss the potential performance improvements of microwave cavities built from
bulk MgB2 materials produced by reactive liquid Mg infiltration.Comment: 7 pages, 2 embedded figures, accepted for publication in Supercond.
Sci. Techno
Comparative Methods for Gene Structure Prediction in Homologous Sequences
The increasing number of sequenced genomes motivates the use of evolutionary patterns to detect genes. We present a series of comparative methods for gene finding in homologous prokaryotic or eukaryotic sequences. Based on a model of legal genes and a similarity measure between genes, we find the pair of legal genes of maximum similarity. We develop methods based on genes models and alignment based similarity measures of increasing complexity, which take into account many details of real gene structures, e.g. the similarity of the proteins encoded by the exons. When using a similarity measure based on an exiting alignment, the methods run in linear time. When integrating the alignment and prediction process which allows for more fine grained similarity measures, the methods run in quadratic time. We evaluate the methods in a series of experiments on synthetic and real sequence data, which show that all methods are competitive but that taking the similarity of the encoded proteins into account really boost the performance
Single-parameter non-adiabatic quantized charge pumping
Controlled charge pumping in an AlGaAs/GaAs gated nanowire by
single-parameter modulation is studied experimentally and theoretically.
Transfer of integral multiples of the elementary charge per modulation cycle is
clearly demonstrated. A simple theoretical model shows that such a quantized
current can be generated via loading and unloading of a dynamic quasi-bound
state. It demonstrates that non-adiabatic blockade of unwanted tunnel events
can obliterate the requirement of having at least two phase-shifted periodic
signals to realize quantized pumping. The simple configuration without multiple
pumping signals might find wide application in metrological experiments and
quantum electronics.Comment: 4 pages, 4 figure
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