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PETROS DIMOPOULOS (University of Rome 'La Sapienza')15/06/2010, 18:00Weak decays and matrix elementsWe present preliminary results on the of neutral kaon oscillations in extensions of the Standard Model. Using $N_f=2$ maximally twisted sea quarks and Osterwalder-Seiler valence quarks, we achieve both O(a)-improvement and continuum-like renormalization pattern for the relevant four-fermion operators. We perform simulations at three values of the lattice spacing and extrapolate/interpolate...Go to contribution page
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Hideo Matsufuru (High Energy Accelerator Research Organization (KEK))15/06/2010, 18:00Chiral symmetryWe investigate the Nc=2 lattice gauge theories with two flavors of the Wilson fermions (and twisted mass ghosts) in fundamental and adjoint representations. The phase structure of these theories is studied in the coupling-quark mass plane by observing meson correlation functions and spectral density of the Dirac operator.Go to contribution page
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Apostolos Skouroupathis (University of Cyprus, Department of Physics)15/06/2010, 18:00Standard model parameters and renormalizationIn this work we compute the one-loop 1PI 2-point perturbative bare Green's functions of: - The fermion propagator $\bar{\Psi} \Psi$ - Local fermion bilinear operators $\bar{\Psi} \Gamma \Psi$ - Extended fermion bilinear operators $\bar{\Psi} \Gamma_{\{\mu} \overleftrightarrow{D}_{\nu\}} \Psi$ where $\Gamma$ corresponds to the Dirac operators and $\overleftrightarrow{D} = \frac{1}{2}\left(...Go to contribution page
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Massimo Di Pierro (DePaul University)15/06/2010, 18:00Algorithms and machinesVis is a system that implements Software as a Service for Lattice QCD computations. At its core it is a repository of gauge confurations with web and web services interfaces. It gives users the ability to queue tasks and execute them in background. Tasks can be FermiQCD program and/or visualization algorithms (topological charge, polyakov lines, evergy density, etc.). The web services are...Go to contribution page
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Terrence Draper (University of Kentucky)15/06/2010, 18:00Chiral symmetryWe champion use of the absolute measure of local chirality since it has a uniform distribution for randomly reshuffled chiral components so that any deviations from uniformity in the associated "X-distribution" are directly attributable to QCD-induced dynamics. We observe a transition in the qualitative behavior of the absolute X-distribution of low-lying eigenmodes which, we propose,...Go to contribution page
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marcello pivanti (INFN and University of Ferrara)15/06/2010, 18:00Algorithms and machinesThis poster covers in details the architecture of the application-driven AuroraScience supercomputer. This machine is a large 3D array of latest generation Intel processors, with nearest-neigbor processors connected by a network with toroidal topology. Each node has a peak (double precision) performance of 100-150 Gflops. This machine has been engineered to be reliably assembled in...Go to contribution page
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Anthony Kennedy (University of Edinburgh), Bálint Joó (JLab), Mike Clark (Harvard University), Paulo Silva (Universidade de Coimbra)15/06/2010, 18:00Algorithms and machinesWe show how to improve the molecular dynamics step of HMC, both by tuning the integrator using Poisson brackets measurements and with the use of force gradient integrators. We show results for moderate lattice sizes.Go to contribution page
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Hinnerk Stueben (Konrad-Zuse-Zentrum fuer Informationstechnik Berlin (ZIB))15/06/2010, 18:00Algorithms and machinesBQCD is a Hybrid Monte-Carlo program that simulates lattice QCD with dynamical Wilson fermions. The development of BQCD began in Berlin in 1998 for studies of parallel tempering and the Aoki phase. For ten years BQCD has been one of the main production programs of the QCDSF collaboration. The program has been ported to and optimised for different massively parallel machines, for...Go to contribution page
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Maria Paola Lombardo (INFN)15/06/2010, 18:00Applications beyond QCDWe study QCD with 12 light flavors at intermediate values of the bare lattice coupling. We contrast and compare the results for the chiral condensate and the the pion mass with different theoretical models motivated by the physics of the Goldstone phase and universal properties of chiral symmetry breaking. Our analysis favors chiral symmetry restoration.Go to contribution page
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Yuji Sakai (Kyushu University)15/06/2010, 18:00Nonzero temperature and densityLattice QCD (LQCD) has the sign problem at real quark chemical potential. There are some regions with no sign problem; one is the imaginary quark chemical potential region and another is the real and imaginary isospin chemical potential regions. We show that the Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model can reproduce LQCD data in the regions. We also determine the parameters...Go to contribution page
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Marina Marinkovic (Humboldt University Berlin)15/06/2010, 18:00Algorithms and machinesMass preconditioned HMC and DD-HMC are among the most popular algorithms to simulate improved Wilson fermions. We present a comparison of the performance of the two algorithms for realistic quark masses and lattice sizes.Go to contribution page
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Alessandro Papa (Università della Calabria and INFN), Mario Gravina (Laboratoire de Physique Théorique, Université de Paris-Sud 1, Orsay1), Roberto Fiore (Università della Calabria and INFN)15/06/2010, 18:00Critical properties of the compact three-dimensional U(1) lattice gauge theory are explored at finite temperatures. The critical point of the deconfinement phase transition, critical indices and the string tension are studied numerically on lattices with temporal extension Nt = 8 and spatial extension ranging from L = 32 to 256. The critical indices, which govern the behaviour across the...Go to contribution page
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Gennaro Cortese (Università della Calabria and INFN-Cosenza)15/06/2010, 18:00Vacuum structure and confinementThe 2D Z(5) vector model is investigated through the determination of critical points and various critical indices. To this purpose, a new cluster algorithm has been developed for 2D Z(N) models with odd values of N. Results are compared with analytical predictions.Go to contribution page
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Swagato Mukherjee (Assistant Physicist)15/06/2010, 18:00Nonzero temperature and densityWe discuss the universal properties of the QCD chiral transition for both zero and small but non-zero chemical potential. We outline how those universal properties can be used to extract the curvature of the line of chiral transitions in the T-\mu plane for small chemical potential. We present evidence of these universal properties and result for this curvature obtained using lattice...Go to contribution page
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Harald Markum (Vienna University of Technology)15/06/2010, 18:00Theoretical developmentsTheories with noncommutative space-time coordinates represent alternative candidates of grand unified theories. We discuss U(1) gauge theory in 2 and 4 dimensions on a lattice with N sites. The mapping to a U(N) plaquette model in the sense of Eguchi and Kawai can be used for computer simulations. In 2D it turns out that the formulation of the topological charge leads to the imaginary part of...Go to contribution page
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Simon Heybrock (University of Regensburg)15/06/2010, 18:00Algorithms and machinesIn analogy to Neubergers double pass algorithm for the Conjugate Gradient inversion with multi-shifts we introduce a double pass variant for BiCGstab(l). A possible application is the Overlap Operator of QCD at non-zero chemical potential, where the kernel of the sign function becomes non-Hermitian. The sign function can be replaced by a partial fraction expansion, requiring multi-shift...Go to contribution page
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Johannes Weber (University of Tsukuba)15/06/2010, 18:00Chiral symmetryMinimally doubled fermions reconcile standard chiral symmetry with a minimal number of flavours in accordance with the restrictions of the Nielsen-Ninomiya no-go theorem. Hypercubic symmetry however, is necessarily broken by the alignment of two poles of the propagator in momentum space. The specified direction of the symmetry breaking strongly affects the properties of these actions....Go to contribution page
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Taegil Bae (Seoul National University, Seoul, Korea (Republic of))15/06/2010, 18:00Weak decays and matrix elementsWe report our first experience with the analysis of $B_K$ calculated on the MILC ultrafine lattices using improved staggered fermions. The results are preliminary. However, since it is so close to the continuum, the prematurity does not desecrate the bright splendor of the results much.Go to contribution page
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Bicudo Pedro (Instituto Superior Técnico, Lisboa)15/06/2010, 18:00Vacuum structure and confinementThe interpretation of the Landau gauge lattice gluon propagator as a massive type bosonic propagator is investigated. This is relevant for the analytical studies of the Landau gauge gluon propagator, since in Lattice QCD we are able to also compute the non-pertubative infrared gluon mass and compute how it matches with the ultraviolet region addressed in pertubative QCD. Our analysis...Go to contribution page
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Huey-Wen Lin (University of Washington)15/06/2010, 18:00Hadronic structure and interactionsWe report a recent breakthrough in lattice QCD calculations of hadron form factors at large momentum transfer. Conventional lattice form-factor calculations typically reach about 2.5 GeV$^2$ or less, but in this work the transfer momentum is pushed as high as 6 GeV$^2$. Our approach can be applied to isotropic lattices and lattices with smaller lattice spacing to calculate even...Go to contribution page
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Georg von Hippel (Institut f. Kernphysik, Uni Mainz)15/06/2010, 18:00Algorithms and machinesWe present an algorithm to automatically derive Feynman rules for lattice perturbation theory in background field gauge. Vertices with an arbitrary number of both background and quantum legs can be derived automatically from both gluonic and fermionic actions. The algorithm is a generalisation of our earlier algorithm based on prior work by L\"uscher and Weisz. We also present techniques...Go to contribution page
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Richard Evans (Universitaet Regensburg)15/06/2010, 18:00Weak decays and matrix elementsWe investigate two alternatives to the Sequential Propagator Method used in Lattice QCD calculations of heavy-light semileptonic form factors. In the first method, which we refer to as the Stochastic Propagator Method, we replace the sequential propagator with a stochastic all-to-all propagator. In the second method, we employ the so called "one-end trick". After minimizing the stochastic...Go to contribution page
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Kenichi Ishikawa (Hiroshima University, Department of Physical Science)15/06/2010, 18:00Algorithms and machinesThe Large Hadron Collider (LHC) experiment has begun to trap the tail of Higgs boson and to find the evidence of a theory beyoned the standerd model (SM). Motivated from the unnatural feature of elementary scalar Higgs field, many models beyond the SM have been proposed and studied. The technicolor (TC) model is one of them and describes the origin of electroweak symmetry breaking...Go to contribution page
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John Laiho (University of Glasgow)15/06/2010, 18:00Weak decays and matrix elementsWe present a new method for determining K->pipi matrix elements from lattice simulations. This method is less costly than direct simulations of K->pipi at physical kinematics, and evades the Maiani-Testa no-go theorem by simulating with both pions at rest. It improves, however, upon the traditional "indirect" approach of constructing the K->pi pi matrix elements using NLO SU(3) ChPT, which...Go to contribution page
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Elisabetta Pallante (University of Groningen)15/06/2010, 18:00Hadron spectroscopyWe discuss the computation of the K and D meson masses in the N_f = 2+1+1 twisted mass lattice QCD setup, where explicit heavy flavour and parity breaking occurs at finite lattice spacing. We present three methods suitable in this context, and verify their consistency.Go to contribution page
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Pedro Bicudo (Instituto Superior Técnico, Lisboa)15/06/2010, 18:00Algorithms and machinesWe discuss the CUDA approach to the simulation of pure gauge Lattice SU(2). CUDA is a hardware and software architecture developed by Nvidia for computing on the GPU. We present an analysis and performance comparison between the GPU and CPU with single precision. Analysis with single and multiple GPU's, using CUDA and OPENMP, are also presented. In order to obtain a high performance,...Go to contribution page
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Michael Creutz (Brookhaven Lab)15/06/2010, 18:00Chiral symmetryMinimally doubled chiral fermions have the unusual property of a single local field creating two fermionic species. Spreading the field over nearby neighbors allows construction of combinations that isolate specific modes. Combining these fields into bilinears produces meson fields of specific quantum numbers.Go to contribution page
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Anne-Mari Mykkänen (University of Helsinki and Helsinki Institute of Physics), Jarno Rantaharju (University of Helsinki and Helsinki Institute of Physics)15/06/2010, 18:00Applications beyond QCDThe research of strongly coupled beyond-the-standard-model theories has generated significant interest in non-abelian gauge field theories with different number of fermions in different representations. Motivated by technicolor scenarios, we study the non-perturbative improvement of the Wilson-clover action using SU(2) gauge fields and fermions in fundamental and adjoint representations. The...Go to contribution page
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Stephan Durr (Wuppertal University and Julich Supercomputing Center)15/06/2010, 18:00Hadron spectroscopyA status report is given for a joint project between the Budapest-Marseille-Wuppertal collaboration and the Regensburg group to study the quark mass-dependence of octet baryons in SU(3) Baryon ChPT. This formulation is expected to extend to larger masses than Heavy-Baryon ChPT. Its applicability will be tested with 2+1 flavor data which cover three lattice spacings and pion masses down to...Go to contribution page
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Jair Wuilloud (uni Bern)15/06/2010, 18:00Chiral symmetryThe investigated theory has one Wilson fermion in the fundamental representation with colour gauge group SU(3). In addition to studying the one flavour theory particle spectrum, we test by Monte-Carlo simulations the existence of a CP-symmetry breaking phase and predictions from the orientifold planar equivalence. The poster also describes the computation of the...Go to contribution page
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Björn Wellegehausen (TPI, University Jena)15/06/2010, 18:00Vacuum structure and confinementG2 is the smallest simple and simply connected lie group with a trivial center. Therefore investigations of G2 gauge theories may help to clarify the relevance of center symmetry for confinement. Beside this it has an intriguing connection to SU(3) gauge theorie and to QCD. If one couples a scalar field in the fundamental representation to the gauge field one can break the G2 gauge symmetry to...Go to contribution page
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Massimo D'Elia (Universita` di Genova & INFN)15/06/2010, 18:00Nonzero temperature and densityWe consider the endpoint of the Roberge-Weiss first order transition line, which is present for imaginary values of the baryon chemical potential, and study its nature in two flavor QCD as a function of the quark masses. We present evidence that the endpoint is first order (hence a triple point) for low quark masses, discuss the fate of the further first order lines departing from it, and...Go to contribution page
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Mushtaq Loan (International School, Jinan University)15/06/2010, 18:00Nonzero temperature and densityWe present results of rho meson mass in lattice QCD with two degenerate flavours of dynamical quarks at finite temperature. Our preliminary results show that the ground state mass remains almost unchanged as the temperature is approaching to the critical temperature from the below. Above T_{c}, we find indication that mesonic excitations survive both at finite quark mass and in the physical limit.Go to contribution page
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Shinji Ejiri (Niigata University)15/06/2010, 18:00Nonzero temperature and densityWe study scaling behavior of a chiral order parameter defined by an axial Ward-Takahashi identity in two-flavor QCD. It has been shown that the scaling behavior of the chiral order parameter agrees with the scaling function of the three-dimensional O(4) spin model by a simulation with the RG (Iwasaki) improved gauge action and clover improved quark action at zero chemical potential. We extend...Go to contribution page
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Waseem Kamleh (University of Adelaide)15/06/2010, 18:00Hadronic structure and interactionsThe effect of a uniform background magnetic field on the wave function of the d-quark in the ground state of the proton is calculated in Lattice QCD. We focus on the wave functions in the Landau and Coulomb gauges. When the quarks are annihilated at different lattice sites, we observe the formation of a scalar u-d diquark pair within the proton in the Landau gauge, which is not present...Go to contribution page
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Claudio Bonati (PI)15/06/2010, 18:00Algorithms and machinesWe will show our implementation of the RHMC algorithm for staggered fermions on Graphics Processing Units using the NVIDIA CUDA programming language. While previous studies exclusively deal with the Dirac matrix inversion problem, our code performs the complete MD trajectory on the GPU. After pointing out the main bottlenecks and how to circumvent them, we discuss the performance of our code.Go to contribution page
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Boram Yoon (Seoul National University)15/06/2010, 18:00Weak decays and matrix elementsWe report a recent progress in determining $B_K$ based on the SU(2) analysis of the data. We use HYP staggered fermions as valence quarks and use asqtad staggered fermions as sea quarks. A number of systematic errors are reviewed in some details.Go to contribution page
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Jangho Kim (Department of Physics and Astronomy, Seoul National University)15/06/2010, 18:00Weak decays and matrix elementsWe report a recent progress in the SU(3) analysis of $B_K$ calculated using improved staggered fermions in a mixed action environment: valence quarks are HYP staggered fermions and sea quarks are asqtad staggered fermions. The systematic errors reviewed in some details.Go to contribution page
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Yong-Chull Jang (Department of Physics and Astronomy, Seoul National University)15/06/2010, 18:00Standard model parameters and renormalizationWe discuss about the systematic errors in $B_K$ calculated on the MILC lattices using improved staggered fermions. We address unresolved issues on the finite volume effect, dependence of $B_K$ on the light sea quark masses, dependence of $B_K$ on the strange sea quark mass, and so on.Go to contribution page
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Monahan Chris (University of Cambridge)15/06/2010, 18:00Standard model parameters and renormalizationWe present a calculation of the b quark mass from lattice NonRelativistic QCD (NRQCD). The b quark mass is extracted using the two-loop NRQCD heavy quark energy shift and mass renormalisation, previously calculated to only one-loop. These parameters are obtained with a hybrid technique: gluonic contributions are extrapolated from a quenched high-beta simulation and the fermionic contributions...Go to contribution page
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Anthony Francis (Universitaet Bielefeld)15/06/2010, 18:00Nonzero temperature and densityWe explore properties of hadronic excitations at high temperature in the chiral limit by investigating hadron correlation functions in the deconfined phase of quenched QCD. This is achieved by performing a systematic analysis of the influence of cut-off effects on light quark meson correlators at $T=1.5 T_c$ using clover improved Wilson fermions on quenched gauge field...Go to contribution page
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Massimo D'Elia (Universita` di Genova & INFN)15/06/2010, 18:00Nonzero temperature and densityWe investigate the properties of the deconfining/chiral restoring transition for two flavor QCD in presence of a uniform background magnetic field. We adopt a standard staggered discretization of the fermion action, different values of the bare quark mass corresponding to pion masses ranging from 200 to 500 MeV, and magnetic fields up to eB = 1 GeV^2. We present first results regarding the...Go to contribution page
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Michela D'Onofrio (University of Helsinki)15/06/2010, 18:00Applications beyond QCDThe baryon number in the Standard Model is violated by non-perturbative sphaleron transitions. At temperatures above the electroweak scale, the rate of the sphaleron transitions is unsuppressed and has been accurately measured using effective theories on the lattice. At temperatures substantially below the electroweak scale, the Higgs field expectation value is large and the sphaleron rate is...Go to contribution page
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Claudio Bonati (PI)15/06/2010, 18:00Vacuum structure and confinementThe numerical implementation of monopole creation operator was pointed out to have problems related to bulk transitions that could possibly affect the interpretation of its mean value as an order parameter for monopole condensation. Preliminary evicence is presented that these unexpected behaviours are in fact only due to lattice artefacts and do not overcome the physical intarpretation of the...Go to contribution page
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Yu Maezawa (RIKEN)15/06/2010, 18:00Nonzero temperature and densityThe viscous coefficients are input of the calculation of the relativistic dissipative hydrodynamics and should be given by a microscopic theory. It is known that the coefficients will be calculated by the Green-Kubo-Nakano (GKN) formula if the fluid is described by the relativistic Navier-Stokes (RNS) equation. However, we cannot apply the RNS theory because this theory is acausal and...Go to contribution page
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Paulo Silva (Center for Computational Physics, University of Coimbra)15/06/2010, 18:00Vacuum structure and confinementThe gluon and ghost propagators are computed using both quenched and dynamical configurations for the same lattice spacings. The Wilson fermions are simulated at several quark masses. Furthermore, the effect of the Gribov copies is evaluated for all sets of configurations.Go to contribution page
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Sara Collins (University of Regensburg)15/06/2010, 18:00Hadronic structure and interactionsWe report on an ongoing project to calculate disconnected contributions to hadronic structure with results on QCDSF dynamical $n_f=2$ configurations at three volumes.Go to contribution page
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