C. Battista

Lattice calculation of D- and B-meson semileptonic decays, using the clover action at β = 6.0 on APE

Abstract We present the results of a high statistics lattice calculation of hadronic form factors relevant for D - and B -meson semi-leptonic decays into light pseudoscalar and vector mesons. The results have been obtained by averaging over 170 gauge field configurations, generated in the quenched approximation, at β = 6.0, on a 18 3 × 64 lattice, using the O ( α )-improved SW-Clover action. From the study of the matrix element 〈 K − |J μ |D 0 〉, we obtain f + (0) = 0.78 ± 0.08 and from the matrix element 〈 K ∗0 |J μ |D + 〉 we obtain V (0) = 1.08 ± 0.22, A i (0) = 0.67 ± 0.11 and A 2 (0) = 0.49 ± 0.34. We also obtain the ratios V(0) A 1 (0) = 1.6 ± 0.3 and A 2 (0) A 1 (0) = 0.7 ± 0.4 . Our predictions for the different form factors are in good agreement with the experimental data, although, in the case of A 2 (0), the errors are still too large to draw any firm conclusion. With the help of the Heavy Quark Effective Theory (HQET) we have also extrapolated the lattice results to B -meson decays. The form factors follow a behaviour compatible with the HQET predictions. Our results are in agreement with a previous lattice calculation, performed at β = 6.4, using the standard Wilson action.

Lbe Simulations Of Rayleigh-Bénard Convection On The Ape100 Parallel Processor

In this paper we describe an implementation of the Lattice Boltzmann Equation method for fluid-dynamics simulations on the APE100 parallel computer. We have performed a simulation of a two-dimensional Rayleigh-Benard convection cell. We have tested the theory proposed by Shraiman and Siggia for the scaling of the Nusselt number vs. Rayleigh number.

A HARDWARE IMPLEMENTATION OF THE APE100 ARCHITECTURE

APE100 processors are based on a simple Single Instruction Multiple Data architecture optimized for the simulation of Lattice Field Theories or other complex physical systems. This paper describes the hardware implementation of the first APE100 machine.

The Software Of The Ape100 Processor

We describe the software environment available for the APE100 parallel processor. We discuss the parallel programming language that we have defined for APE100 and its optimizing compiler. We then describe the operating system that allows to control APE100 from a host computer.

A high statistics lattice calculation of ƒB in the static limit on APE

We present a high statistics calculation of ƒB in the static limit. The results have been obtained by numerical simulation of quenched QCD, at β = 6.0 on a 183 × 32 lattice. We compare ƒB calculated by using the Wilson and the Clover quark actions. The decay constant is obtained by studying heavy-light correlation functions of different smeared operators, on a sample of 210 gauge field configurations. We find that cubic smearings of size Ls ⩽ 3 or Ls ⩾ 9 are bad projectors on the lightest pseudoscalar state. Combining the information coming from smearing Ls = 5 and Ls = 7, we have obtained ƒB = 370±40 MeV in the clover case and ƒB = 350±40±30 MeV in the Wilson case. Our results support a large value of the pseudoscalar decay constant in the static approximation.

A lattice study of the exclusive B->K*gamma decay amplitude, using the Clover action at beta=6.0

Abstract We present the results of a numerical calculation of the B → K ∗ γ form factors. The results have been obtained by studying the relevant correlation functions at β = 6.0, on an 18 3 × 64 lattice, using the O ( a )-improved fermion action, in the quenched approximation. From the study of the matrix element 〈K ∗ | s σ μν b|B〉 we have obtained the form factor T 1 (0) which controls the exclusive decay rate. The results are compared with the recent results from CLEO. We also discuss the compatibility between the scaling laws predicted by the Heavy Quark Effective Theory (HQET) and pole dominance, by studying the mass- and q 2 -dependence of the form factors. From our analysis, it appears that the form factors follow a mass behaviour compatible with the predictions of the HQET and that the q 2 -dependence of T 2 is weaker than would be predicted by pole dominance.

The teraflop supercomputer APEmille: architecture, software and project status report*

Abstract APEmille is a SPMD parallel processor under development at INFN, Italy, in cooperation with DESY, Germany. APEmille is suited for grand challenges computational problems such as QCD simulations, climate modelling, neural networks, computational chemistry, numerical wind tunnels, seismic and combustion simulations. Its 1 Teraflop/s peak performance and its architecture, together with its language features, allow such applications to execute effectively. APEmille is based on an array of custom arithmetic processors arranged on a tridimensional torus. The processor is optimized for complex computations and has a peak performance of 528 Mflop at 66 MHz. Each processing element has 8 Mbytes of locally addressable RAM. On the software side particular emphasis is devoted to the programming languages that will be available (TAO and C++) and their object oriented, dynamic characteristics: with TAO it is possible to develop language extensions similar to the usual HEP notation; with C++ the portability from and towards different platforms is made possible.

An overview of the APEmille parallel computer

We describe the architecture of the APEmille Parallel Computer, the new generation of the APE family of processors optimized for Lattice Gauge Theory simulations. We emphasize the features of the new machine potentially useful for applications in other areas of computational physics.

Status of APE projects

Abstract This talk is divided in two parts. In the first part, we will summarize the status of the APEmille project that will be completed by the end of the year. We will then devote the rest of the talk to the description of a new project for a multi-TeraFlop machine, apeNEXT. The interested reader will find a much more detailed discussion of all the items touched upon here in the full proposal of the project that will shortly appear on hep-lat.

The new wave of the APE project: APEmille

We describe APEmille, the latest generation of the APE parallel processors. This machine, an evolution of the APE100 concept, is very efficient for LGT simulations as well as for a broader class of applications requiring massive floating point computations. Several new features characterise this evolution. In particular local addressing capabilities are added to all computing nodes. APEmille also exhibits a higher degree of integration with a network of workstations acting as a global host system. An APEmille system in the Teraflops range will be completed in three-four years. The architecture proposed in this paper is being currently simulated and evaluated.