Static quarks with improved statistical precision

We present a numerical study for different discretisations of the static action, concerning cut-off effects and the growth of statistical errors with Euclidean time. An error reduction by an order of magnitude can be obtained with respect to the Eichten-Hill action, for time separations beyond 1.3 fm, keeping discretization errors small. The best actions lead to a big improvement on the precision of the quark mass Mb and F_Bs in the static approximation.Comment: 3 pages, 4 figures, Lattice2003(heavy

Towards a precision computation of f_Bs in quenched QCD

We present a computation of the decay constant f_Bs in quenched QCD. Our strategy is to combine new precise data from the static approximation with an interpolation of the decay constant around the charm quark mass region. This computation is the first step in demonstrating the feasability of a strategy for f_B in full QCD. The continuum limits in the static theory and at finite mass are taken separately and will be further improved.Comment: Lattice2003(heavy), 3 pages, 2 figure

Improved interpolating fields in the Schroedinger functional

The general aim of this thesis is to probe several methods to extract low-energy quantities (masses, decay constants,...) more reliably in lattice gauge theory. We will investigate how to suppress contributions to correlation functions from the first excited meson state. We will show how to construct so-called improved meson interpolating fields, as they have only small contributions from the first excited meson state, from a basis of interpolating fields at the Schroedinger functional boundaries. The variational principle is applied to correlation matrices that are built up from boundary-to-boundary correlation functions. It will deliver information about the lowest-lying meson states in the considered channel. We also investigate the possibility to cancel the first excited state contribution by means of an alternative method. Moreover, an alternative way to extract the mass gap between the ground and the first excited state will be presented. Monte-Carlo simulations at several lattice spacings are performed in the 'quenched approximation'. Spectral properties of light-light and static-light pseudoscalar mesons are investigated. The first type is realised by two mass-degenerate quarks at about the strange quark mass, the second type by a light quark with the mass of the strange quark and an infinitely heavy b-quark. The light-light channel describes unphysically heavy pions and the static-light one is an approximation for the B_s-meson. The investigation of the latter case is particularly interesting since so-called B-factories, such as BaBar and Belle, are gathering physical information about masses, decay modes and CP-violating effects in the B-meson system. (orig.)SIGLEAvailable from: http://deposit.ddb.de/cgi-bin/dokserv?idn=972644628 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Smart Antenna Terminal - SANTANA

The demand for broadband data communication will increase rapidly in the next years. Satellite systems offer unique possibilities to connect professional mobile users to broadband data networks and services. The targeted markets are users on aircraft, ships and cars. High bandwidths must be utilized to realize the projected high data rates. Therefore, the attention of system providers will eventually move to systems operating in the Ka-band. The terminal antennas must meet complex requirements like high antenna gain, fast target acquisition and tracking, interferer cancellation and handling of several satellites at the same time. Here, smart antenna terminals employing digital beamforming are most promising. These antennas are very flexible and can be reconfigured easily to new mission profiles. The goal of the project Smart Antenna Terminal was the development, realization and test of demonstrators of broadband terminal antennas using digital beamforming in the Ka-band. These demonstrators can be used as building blocks for larger terminal antennas

Lattice HQET with exponentially improved statistical precision

We modify the Eichten-Hill action of static quarks on the lattice in order to achieve a reduction of statistical errors but retaining the O(a)-improvement properties of that action. Statistical fluctuations are reduced by a factor which grows exponentially with Euclidean time, x_0. For the first time, B-meson correlation functions are computed with good statistical precision in the static approximation for x_0 >1 fm. At lattice spacings a#approx#0.1 fm, a#approx#0.08 fm and a#approx#0.07 fm the B_s-meson decay constant is determined in static and quenched approximations. A correction due to the finite mass of the b-quark is estimated by combining these static results with a recent determination of F_D__s (orig.)SIGLEAvailable from TIB Hannover: RA 2999(03-087) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Static quarks with improved statistical precision

We present a numerical study for different discretisations of the static action, concerning cut-off effects and the growth of statistical errors with Euclidean time. An error reduction by an order of magnitude can be obtained with respect to the Eichten-Hill action, for time separations up to 2 fm, keeping discretization errors small. The best actions lead to a big improvement on the precision of the quark mass M_b and F_B__s in the static approximation. (orig.)Available from TIB Hannover: RA 2999(03-139) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDeutsche Forschungsgemeinschaft (DFG), Bonn (Germany)DEGerman