Thu·Sep 5, 2002Thursday·September 5, 2002

1. 01*

   Non-perturbative scale evolution of four-fermion operators

   M. Guagnelli🇮🇹 · J. Heitger🇩🇪 · C. Pena🇮🇹 · S. Sint🇨🇭 · A. Vladikas🇮🇹

   We apply the Schroedinger Functional (SF) formalism to determine the renormalisation group running of four-fermion operators which appear in the effective weak Hamiltonian of the Standard Model. Our calculations are done using Wilson fermions and the parity-odd components of the operators. Preliminary results are presented for the operator $O_{VA}=(\bar{s}{\gamma }_{\mu }d)(\bar{s}{\gamma }_{\mu }{\gamma }_{5}d)$.

   hep-latNucl.Phys.B Proc.Suppl.(2003)·14 citations
2. 02*

   Zone methods and the fermion sign problem

   Dean Lee (NC State)🇺🇸

   We review a recently proposed approach to the problem of alternating signs for fermionic many body Monte Carlo simulations in finite temperature simulations. We derive an estimate for fermion wandering lengths and introduce the notion of permutation zones, special regions of the lattice where identical fermions may interchange and outside of which they may not. Using successively larger permutation zones, one can extrapolate to obtain thermodynamic observables in regimes where direct simulation is impossible.

   hep-latNucl.Phys.B Proc.Suppl.(2003)·2 citations
3. 03*

   Static Potential and Local Color Fields in Unquenched Three-Dimensional Lattice QCD

   Howard D. Trottier🇨🇦 · Kit Yan Wong🇨🇦

   String breaking by dynamical quarks in (2+1)-d lattice QCD is demonstrated in this project, by measuring the static potential and the local color-electric field strength between a heavy quark and antiquark pair at large separations. Simulations are done for unquenched SU(2) color with two flavors of staggered quarks. An improved gluon action is used which allows simulations to be done on coarse lattices, providing an extremely efficient means to access the quark separations and propagation times at which string breaking occurs. The static quark potential is extracted using only Wilson loop operators and hence no valence quarks are present in the trial states. Results give unambiguous evidence for string breaking as the static quark potential completely saturates at twice the heavy-light meson mass at large separations. It is also shown that the local color-electric field strength between the quark pair tends toward vacuum values at large separations. Implications of these results for unquenched simulations of QCD in 4-d are drawn.

   hep-latNucl.Phys.B Proc.Suppl.(2003)·7 citations
4. 04*

   Hybrid mesons from anisotropic lattice QCD with the clover and improved gauge actions

   Xiang-Qian Luo🇨🇳 · Zhong-Hao Mei (Zhongshan Univ., China)🇨🇳

   We study hybrid mesons from the clover and improved gauge actions at $\beta =2.6$ on the anisotropic $12^3\times 36$ lattice using our PC cluster. We estimate the mass of $1^{-+}$ light quark hybrid as well as the mass of the charmonium hybrid. The improvement of both quark and gluonic actions, first applied to the hybrid mesons, is shown to be more efficient in reducing the lattice spacing and finite volume errors.

   hep-lathep-phNucl.Phys.B Proc.Suppl.(2003)·15 citations
5. 05*

   Topological susceptibility with the improved Asqtad action

   MILC Collaboration: C. Bernard (Washington U)🇺🇸 · T. Burch (U Arizona)🇺🇸 · T.A. DeGrand (U Colorado)🇺🇸 · C.E. DeTar (U Utah)🇺🇸 · Steven Gottlieb (U Indiana)🇺🇸 · E. Gregory (U Arizona)🇺🇸 · A. Hasenfratz (U Colorado)🇺🇸 · U.M. Heller (CSIT FSU)🇺🇸 · J. Hetrick (U Pacific)🇺🇸 · J. Osborn (U Utah)🇺🇸 · R.L. Sugar (UC Santa Barbara)🇺🇸 · D. Toussaint (U Arizona)🇺🇸

   As a test of the chiral properties of the improved Asqtad (staggered fermion) action, we have been measuring the topological susceptibility as a function of quark masses for 2 + 1 dynamical flavors. We report preliminary results, which show reasonable agreement with leading order chiral perturbation theory for lattice spacing less than 0.1 fm. The total topological charge, however, shows strong persistence over Monte Carlo time.

   hep-latNucl.Phys.B Proc.Suppl.(2003)·6 citations
6. 06*

   Static hybrid quarkonium potential with improved staggered quarks

   MILC Collaboration: C. Bernard (Washington U)🇺🇸 · T. Burch (U Arizona)🇺🇸 · C.E. DeTar (U Utah)🇺🇸 · Ziwen Fu (U Utah) · Steven Gottlieb (U Indiana)🇺🇸 · E. Gregory (U Arizona)🇺🇸 · U.M. Heller (CSIT FSU)🇺🇸 · J. Osborn (U Utah)🇺🇸 · R.L. Sugar (UC Santa Barbara)🇺🇸 · D. Toussaint (U Arizona)🇺🇸

   We are studying the effects of light dynamical quarks on the excitation energies of a flux tube between a static quark and antiquark. We report preliminary results of an analysis of the ground state potential and the ${\Sigma }_g^{\prime +}$ and ${\Pi }_u$ potentials. We have measured these potentials on closely matched ensembles of gauge configurations, generated in the quenched approximation and with 2+1 flavors of Asqtad improved staggered quarks.

   hep-latNucl.Phys.B Proc.Suppl.(2003)·9 citations
7. 07*

   Chiral symmetry breaking in (2+1) dimensional QED

   Pieter Maris🇺🇸 · Dean Lee🇺🇸

   We study dynamical mass generation in QED in (2+1) dimensions using Hamiltonian lattice methods. We use staggered fermions, and perform simulations with explicit dynamical fermions in the chiral limit. We demonstrate that a recently developed method to reduce the fermion sign problem can successfully be applied to this problem. Our results are in agreement with both the strong coupling expansion and with Euclidean lattice simulations.

   hep-latNucl.Phys.B Proc.Suppl.(2003)·4 citations
8. 08*

   Mollified Monte Carlo

   D.D. Ferrante🇺🇸 · J. Doll🇺🇸 · G.S. Guralnik🇺🇸 · D. Sabo🇺🇸

   Using a common technique for approximating distributions [generalized functions], we are able to use standard Monte Carlo methods to compute QFT quantities in Minkowski spacetime, under phase transitions, or when dealing with coalescing stationary points.

   hep-latmath-phmath.MPphysics.comp-phNucl.Phys.B Proc.Suppl.(2003)·5 citations
9. 09*

   Lattice QCD at finite isospin chemical potential and temperature

   J.B. Kogut🇺🇸 · D.K. Sinclair🇺🇸

   We simulate lattice QCD at a finite chemical potential ${\mu }_I$ for isospin ($I_3$) at zero and finite temperatures. At some ${\mu }_I={\mu }_c$ QCD has a second order transition with mean-field critical exponents to a state where ($I_3$) is broken spontaneously by a charged pion condensate. Heating the system with ${\mu }_I>{\mu }_c$ we find there is some temperature at which this condensate evaporates. This transition appears to be second order and mean-field at lower ${\mu }_I$ values, and first order for ${\mu }_I$ sufficiently large. We are determining the dependence of the finite temperature crossover $T_c$ on ${\mu }_I$ for ${\mu }_I<{\mu }_c$. This is expected to be identical to $T_c$'s dependence on quark-number chemical potential ${\mu }_q$ for small ${\mu }_q$.

   hep-latNucl.Phys.B Proc.Suppl.(2003)·18 citations
10. 10*

    Study of stochastic estimates of quark loops with unbiased subtraction

    Nilmani Mathur🇺🇸 · Shao-Jing Dong🇺🇸

    Stochastic noise estimator method is a powerful tool to calculate the disconnected insertion involving quark loops. We study the variance reduction technique with unbiased subtraction. We use the complex $Z_2$ noise to calculate the quark loops on a $16^3\times 24$ lattice with $\beta =6.0$ and $\kappa$ = 0.154. Unbiased subtraction method is performed by using hoping parameter expansion. We report on the variance reduction for the point-split vector current as a function of the number of subtraction terms and the number of noise used.

    hep-latNucl.Phys.B Proc.Suppl.(2003)·10 citations
11. 11*

    I=2 Pion Scattering Phase Shift with Wilson Fermions

    CP-PACS Collaboration : S. Aoki🇯🇵 · M. Fukugita🇯🇵 · S. Hashimoto🇯🇵 · K-I. Ishikawa🇯🇵 · N. Ishizuka🇯🇵 · Y. Iwasaki🇯🇵 · K. Kanaya🇯🇵 · T. Kaneko🇯🇵 · Y. Kuramashi🇯🇵 · V. Lesk🇯🇵 · M. Okawa🇯🇵 · Y. Taniguchi🇯🇵 · A. Ukawa🇯🇵 · T. Yoshié🇯🇵

    We present results of phase shift for I=2 $S$-wave $\pi \pi$ system with the Wilson fermions in the quenched approximation. The finite size method proposed by Lüscher is employed, and calculations are carried out at $\beta =5.9$ ($a^{-1}=1.934(16)$ GeV from $m_{\rho }$) on $24^3\times 60$, $32^3\times 60$, and $48^3\times 60$ lattices.

    hep-latNucl.Phys.B Proc.Suppl.(2003)·8 citations
12. 12*

    Light hadron spectrum with two flavors of $O(a)$ improved dynamical quarks : final results from JLQCD

    JLQCD Collaboration: T. Kaneko🇯🇵 · S. Aoki🇯🇵 · R. Burkhalter🇯🇵 · M. Fukugita🇯🇵 · S. Hashimoto🇯🇵 · K-I. Ishikawa🇯🇵 · N. Ishizuka🇯🇵 · Y. Iwasaki🇯🇵 · K. Kanaya🇯🇵 · Y. Kuramashi🇯🇵 · M. Okawa🇯🇵 · N. Tsutsui🇯🇵 and 3 other authors

    We present the final results of the JLQCD calculation of the light hadron spectrum and quark masses with two flavors of dynamical quarks using the plaquette gauge action and fully $O(a)$-improved Wilson quark action at $\beta =5.2$. We observe that sea quark effects lead to a closer agreement of the strange meson and baryon masses with experiment and a reduction of quark masses by about 25.

    hep-latNucl.Phys.B Proc.Suppl.(2003)·4 citations
13. 13*

    Study of unstable particle through the spectral function in O(4) ${\varphi }^4$ theory

    N. Ishizuka🇯🇵 · T. Yamazaki🇯🇵

    We test application of the maximum entropy method to decompose the states contributing to the unstable $\sigma$ correlation function through the spectral function in the four dimensional O(4) ${\varphi }^4$ theory. Reliable results are obtained for the $\sigma$ mass and two-particle $\pi \pi$ state energy using only the $\sigma$ correlation function. We also find that the property of the $\sigma$ particle is different between the unstable ($m_{\sigma }/m_{\pi }>2$) and stable ($m_{\sigma }/m_{\pi }<2$) cases.

    hep-latNucl.Phys.B Proc.Suppl.(2003)·1 citation
14. 14*

    Bayesian approach to the first excited nucleon state in lattice QCD

    S. Sasaki🇯🇵 · K. Sasaki🇯🇵 · T. Hatsuda (Univ. of Tokyo)🇯🇵 · M. Asakawa (Kyoto Univ.)🇯🇵

    We present preliminary results from the first attempt to reconstruct the spectral function in the nucleon and $\Delta$ channels from lattice QCD data using the maximum entropy method (MEM). An advantage of the MEM analysis is to enable us to access information of the excited state spectrum. Performing simulations on two lattice volumes, we confirm the large finite size effect on the first excited nucleon state in the lighter quark mass region.

    hep-latNucl.Phys.B Proc.Suppl.(2003)·21 citations
15. 15*

    Vortex free energies in SO(3) and SU(2) lattice gauge theory

    Philippe de Forcrand🇨🇭 · Oliver Jahn🇨🇭

    Lattice gauge theories with gauge groups SO(3) and SU(2) are compared. The free energy of electric twist, an order parameter for the confinement-deconfinement transition which does not rely on centre-symmetry breaking, is measured in both theories. The results are used to calibrate the scale in SO(3).

    hep-latNucl.Phys.B Proc.Suppl.(2003)·5 citations
16. 16*

    An exact Polynomial Hybrid Monte Carlo algorithm for dynamical Kogut-Susskind fermions

    JLQCD Collaboration: K-I. Ishikawa🇯🇵 · M. Fukugita🇯🇵 · S. Hashimoto🇯🇵 · N. Ishizuka🇯🇵 · Y. Iwasaki🇯🇵 · K. Kanaya🇯🇵 · Y. Kuramashi🇯🇵 · M. Okawa🇯🇵 · N. Tsutsui🇯🇵 · A. Ukawa🇯🇵 · N. Yamada🇯🇵 · T. Yoshié🇯🇵

    We present a polynomial Hybrid Monte Carlo (PHMC) algorithm as an exact simulation algorithm with dynamical Kogut-Susskind fermions. The algorithm uses a Hermitian polynomial approximation for the fractional power of the KS fermion matrix. The systematic error from the polynomial approximation is removed by the Kennedy-Kuti noisy Metropolis test so that the algorithm becomes exact at a finite molecular dynamics step size. We performed numerical tests with $N_f$$=$2 case on several lattice sizes. We found that the PHMC algorithm works on a moderately large lattice of $16^4$ at $\beta$$=$5.7, $m$$=$0.02 ($m_{\mathrm{PS}}/m_{\mathrm{V}}$$\sim$0.69) with a reasonable computational time.

    hep-latNucl.Phys.B Proc.Suppl.(2003)·0 citations
17. 17*

    The ground state of three quarks

    C. Alexandrou (Univ. of Cyprus)🇨🇾 · Ph. de Forcrand (ETH Zurich and CERN)🇨🇭 · O. Jahn (ETH Zurich)🇨🇭

    We measure the static three-quark potential in SU(3) lattice gauge theory with improved accuracy, by using all available technical refinements, including Luscher-Weisz exponential variance reduction. Together with insight gained from 3-state Potts model simulations, our results allow us to sort out the merits of the Delta- and Y-ansaetze.

    hep-latNucl.Phys.B Proc.Suppl.(2003)·138 citations
18. 18*

    Masses of singlet and non-singlet 0++ particles

    UKQCD Collaboration: Alistair Hart🇬🇧 · Craig McNeile🇬🇧 · Chris Michael🇬🇧

    We compute the mass of the singlet 0++ state using both (psi_bar psi) and Wilson loop operators from a N_f=2 lattice QCD calculation.

    hep-latNucl.Phys.B Proc.Suppl.(2003)·36 citations
19. 19*

    Recent results using all-point quark propagators

    A. Duncan🇺🇸 · E. Eichten🇺🇸 · J. Yoo🇺🇸

    Pseudofermion methods for extracting all-point quark propagators are reviewed, with special emphasis on techniques for reducing or eliminating autocorrelations induced by low eigenmodes of the quark Dirac operator. Recent applications, including high statistics evaluations of hadronic current correlators and the pion form factor, are also described.

    hep-latNucl.Phys.B Proc.Suppl.(2003)·1 citation
20. 20*

    Spectrum of SU(2) SUSY Yang-Mills Theory with a light gluino

    R. Peetz🇩🇪 · F. Farchioni🇩🇪 · C. Gebert🇩🇪 · G. Münster🇩🇪

    We report on new results for the low lying spectrum of N=1 SUSY Yang-Mills Theory with SU(2) as the gauge group. Simulating on larger lattices at \kappa = 0.194 and \beta = 2.3, we slowly approach the supersymmetric limit at m_{gluino} = 0.

    hep-latNucl.Phys.B Proc.Suppl.(2003)·21 citations
21. 21*

    Chiral logs with staggered fermions

    C. Aubin🇺🇸 · C. Bernard🇺🇸 · C. DeTar🇺🇸 · Steven Gottlieb🇺🇸 · Urs M. Heller🇺🇸 · K. Orginos🇺🇸 · R. Sugar🇺🇸 · D. Toussaint🇺🇸

    We compute chiral logarithms in the presence of "taste" symmetry breaking of staggered fermions. The lagrangian of Lee and Sharpe is generalized and then used to calculate the logs in $\pi$ and $K$ masses. We correct an error in Ref. [1] [C. Bernard, hep-lat/0111051]; the issue turns out to have implications for the comparison with simulations, even at tree level. MILC data with three light dynamical flavors can be well fit by our formulas. However, two new chiral parameters, which describe order $a^2$ hairpin diagrams for taste-nonsinglet mesons, enter in the fits. To obtain precise results for the physical coefficients at order $p^4$, these new parameters will need to be bounded, at least roughly.

    hep-latNucl.Phys.B Proc.Suppl.(2003)·21 citations
22. 22*

    Gauge-invariant two- and three- density correlators

    C. Alexandrou (Univ. Cyprus)🇨🇾 · Ph. de Forcrand (CERN and ETHZ)🇨🇭 · A. Tsapalis (Univ. Wuppertal)🇩🇪

    Gauge-invariant spatial correlations between two and three quarks inside a hadron are measured within quenched and unquenched QCD. These correlators provide information on the shape and multipole moments of the pion, the rho, the nucleon and the $\Delta$.

    hep-latnucl-exnucl-thNucl.Phys.B Proc.Suppl.(2003)·9 citations
23. 23*

    Gluon propagator and confinement scenario in Coulomb gauge

    Attilio Cucchieri🇧🇷 · Daniel Zwanziger🇺🇸

    We present numerical results in SU(2) lattice gauge theory for the instantaneous part of the gluon propagator in Coulomb gauge D_{44, inst} = V_{coul}(R) \delta(t). Data are taken on lattice volumes 24^4 and 28^4 for 7 values of beta in the interval $2.2\le beta\le 2.8$. The data are confronted with the confinement scenario in Coulomb gauge. They are consistent with a linearly rising color-Coulomb potential V_{coul}(R).

    hep-latNucl.Phys.B Proc.Suppl.(2003)·31 citations
24. 24*

    Staggered Fermion Thermodynamics using Anisotropic Lattices

    L. Levkova🇺🇸

    Numerical simulations of full QCD on anisotropic lattices provide a convenient way to study QCD thermodynamics with fixed physics scales and reduced lattice spacing errors. We report results from calculations with 2-flavors of dynamical fermions where all bare parameters and hence the physics scales are kept constant while the temperature is changed in small steps by varying only the number of the time slices. The results from a series of zero-temperature scale setting simulations are used to determine the Karsch coefficients and the equation of state at finite temperatures.

    hep-latNucl.Phys.B Proc.Suppl.(2003)·2 citations
25. 25*

    Using Approximating Polynomials in Partial-Global Dynamical Simulations

    Andrei Alexandru🇺🇸 · Anna Hasenfratz🇺🇸

    Smeared link fermionic actions can be straightforwardly simulated with partial-global updating. The efficiency of this simulation is greatly increased if the fermionic matrix is written as a product of several near-identical terms. Such a break-up can be achieved using polynomial approximations for the fermionic matrix. In this paper we will focus on methods of determining the optimum polynomials.

    hep-latNucl.Phys.B Proc.Suppl.(2003)·5 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.