Lattice QCD Production on a Commodity Cluster at Fermilab

Large scale QCD Monte Carlo calculations have typically been performed on either commercial supercomputers or specially built massively parallel computers such as Fermilab's ACPMAPS.Commodity clusters equipped with high performance networking equipment present an attractive alternative,achieving superior performance to price ratios and offering clear upgrade paths.We describe the construction and results to date of Fermilab's prototype production cluster,which consists of 80 dual Pentium Ⅲsystems interconnected with Myrinet networking hardware.We describe software tools and techniques we have developed for operating system installation and administration.We discuss software optimizations using the Pentium's built-in parallel computation facilities(SSE),Finally,we present short and long term plans for the construction of larger facilities.

Study of Topological Structure of Vacuum by Lattice QCD

Overlap fermions and improved 5Li cooling are compared, which exhibits that these two filter methods can produce similar structures. Then the overlap fermions and improved 5Li cooling are combined to calculate the topological charge and identify the structure of the vacuum. The results are consistent with instanton liquid model .

Strange Meson Photo-production and Its Associated Radiative Capture on Proton in Low-Energy QCD Lagrangian

Based on the low energy QCD Lagrangian theory and the crossing symmetry relation, strange meson photoproduction and its associated radiative capture on the proton are investigated in the [SUSF（6） × O（3）]sym . × SUc（3） quark mode/of baryon structure with only one same input parameter, the only strong coupling constant aM. Calculations for the cross sections, p-polarization of γ ＋ P → K^＋ ＋ A reaction and the branching ratios for K^- radiative capture of K^- ＋ p → γ ＋ Y with Y = A, ∑^0 are performed. Good agreements to data are obtained and the results show that, compared to traditional phenomenological models, the low energy QCD Lagrangian theory provides a successful, unifled description of the strange meson photo-production and its associated radiative capture.

Data Transfer Using Buffered I／O API with HPSS

The new KEK Central computer system employed HPSS for data management To gain high performance access to HPSS easily,we built a wrapper of the client APL.

A Lattice Study of the Glueball Spectrum

Glueball spectrum is studied using an improved gluonic action on asymmetric lattices in the pure gauge theory. The smallest spatial lattice spacing is about 0.08 fm which makes the extrapolation to the continuum limit more reliable. In particular, attention is paid to the scalar glueball mass which is known to have problems in the extrapolation. Converting our lattice results to physical units using the scale set by the static quark potential, we obtain the following results for the glueball masses: for the scalar glueball mass and for the tensor glueball.

Vector Meson Mass in Finite Density and Temperature Lattice QCD

Vector meson mass values are studied at finite chemical potential and temperature in lattice QCD with lattice size of 24 × 122× 6 using two flavors of staggered quarks. The investigation focuses on the change of the vector meson mass in the critical region close to T c with two different types of chemical potentials switched on: the isoscalar chemical potential μS and its isovector counterpart μV. It is found that the vector meson mass increases in the QGP phase with both chemical potentials and decreases with μS in the confinement phase.

Two Higgs Doublet Model Ⅲ and Double-Lepton Polarization Asymmetries in Λ_b →Λμ^+μ^- Decays

Using the form factors calculated both in lattice QCD and HQET, we analyze the branching ratio, doublelepton polarization asymmetries and averaged double-lepton polarization asymmetries of Λ_b →Λμ^+μ^- decay in the2 HDM Ⅲ, respectively. Combining the experimental constrains on the 2HDM Ⅲ parameters, we take two set of representative parameter spaces in our calculations. For the branching ratio of Λ+b →Λμμ-decay, considering the uncertainties of the form factors and input parameters, we find the results of both SM and 2HDM Ⅲ can satisfy the current experimental data in the framework of lattice QCD, but not in HQET. Then we calculate the double-lepton polarization asymmetries Pij and their averaged values Pij, we find the double-lepton polarization asymmetries PLT,PNN, and PTT are sensitive to the 2HDM Ⅲ. However, PLN, PNL, PNT, and PTN show the opposite results. The contribution of the 2HDM Ⅲ to their averaged values have similar results.

Predicting the D_(s)(*)D_(s)(*)bound states as the partners of X(3872)

In this work,we investigate the SU(3)flavor symmetry,heavy quark spin symmetry and their breaking effects in the di-meson systems.We prove the existence of the[D_(s)(*)D_(s)(*)]^(0++),[D_(s)(*)D_(s)(*)]^(1++),and[D_(s)(*)D_(s)(*)]^(1++)bound states as the consequence of two prerequisites in the SU(3)flavor symmetry and heavy quark spin symmetry.The first prerequisite,the X(3872)as the weakly D*D=DD*bound state is supported by its mass and decay branching ratios.The second prerequisite,the existence of the DsDs[D_(s)(*)D_(s)(*)]^(0++)bound state is supported by the lattice QCD calculation and the observation of X_(c0)(3930)by the LHCb Collaboration.We hope the future experimental analyses can search for these bound states in the B→[D_(s)(*)D_(s)(*)]h processes(h denotes the light hadrons).The[D_(s)(*)D_(s)(*)]^(0++)bound state is also expected to be reconstructed in the J/ψФinal state in the B→//ψФK decay.