P. Forcrand - Academia.edu (original) (raw)
Papers by P. Forcrand
Journal of High Energy Physics, 2003
We study charmonium using the standard relativistic formalism in the quenched approximation, on a... more We study charmonium using the standard relativistic formalism in the quenched approximation, on a set of lattices with isotropic lattice spacings ranging from 0.1 to 0.04 fm. We concentrate on the calculation of the hyperfine splitting between η c and J/ψ, aiming for a controlled continuum extrapolation of this quantity. The splitting extracted from the non-perturbatively improved clover Dirac operator shows very little dependence on the lattice spacing for a ≤ 0.1fm. The dependence is much stronger for Wilson and tree-level improved clover operators, but they still yield consistent extrapolations if sufficiently fine lattices, a ≤ 0.07 fm (aM(η c ) ≤ 1), are used. Our result for the hyperfine splitting is 77(2)(6) MeV (where Sommer's parameter, r 0 , is used to fix the scale). This value remains about 30% below experiment. Dynamical fermions and OZI-forbidden diagrams both contribute to the remainder. Results for the η c and J/ψ wave functions are also presented.
Progress of Theoretical Physics Supplement, 1996
We present the Japanese-European QCD-TARO collaboration. We discuss the hardware basis and the co... more We present the Japanese-European QCD-TARO collaboration. We discuss the hardware basis and the concept of analyses and present selected results. We comment on the chances and bottlenecks connected to the non-local, international character of the collaboration.
Physics Letters B, 2005
The properties of hadron screening masses around the deconfinement phase transition at finite bar... more The properties of hadron screening masses around the deconfinement phase transition at finite baryonic density can be studied by evaluating the Taylor coefficients with respect to the iso-scalar (µS = µu = µ d ) and iso-vector (µV = µu = −µ d ) chemical potentials, where µu and µ d are u and d quark chemical potentials. We simulate 2-flavour lattice QCD with staggered fermions on a 12 2 × 24 × 6 lattice with ma = 0.05 and 0.10 and report investigations of nucleon, pseudo-scalar and vector mesons. We present new, strong evidence that in the confining phase, the screening masses at µ = 0 have significant temperature dependence, but the effect of µS is very small. Above the critical temperature, the second derivative terms of mesons rapidly increase as contrasted to the case of baryon. We also study the responses of the screening masses to an iso-vector chemical potential and discuss some of the issues related to the properties of hadron masses at finite µ.
Nuclear Physics B - Proceedings Supplements, 1994
ABSTRACT We briefly summarize our results of quenched Wilson hadron spectroscopy at β = 6.3 on a ... more ABSTRACT We briefly summarize our results of quenched Wilson hadron spectroscopy at β = 6.3 on a 323 × 48 lattice. The spectrum of pseudo scalar and vector mesons, (1/2)+ and (3/2)+ baryons composed of up, down, strange and charm quarks are presented. A decrease of mass splitting between (1/2)+ and (3/2)+ baryons is observed when heavy quark masses increase, as in the case of the mass difference between pseudo scalar and vector masses.
Nuclear Physics B - Proceedings Supplements, 1993
Quenched Wilson hadron spectroscopy at fl = 6.3 has been studied by using parallel computer AP100... more Quenched Wilson hadron spectroscopy at fl = 6.3 has been studied by using parallel computer AP1000. Spectrum of hadrons composed of various combinations of hopping parameters are measured on 32 s × 48 and 163 )<48 lattices. We report results of spatial size effects based on various hadron masses. Dependence on boundary conditions along the temporal direction is also examined and discussed.
Journal of Physics A: Mathematical and General, 1988
We study by Monte Carlo simulations, using two different algorithms, the Edwards walk in two dime... more We study by Monte Carlo simulations, using two different algorithms, the Edwards walk in two dimensions and extract its critical exponents. We establish that the fractal dimension computed in terms of critical exponents is different from the HausdorR dimension computed by measure-theoretic methods.
Nuclear Physics B- …, 1999
To elucidate the role played by instantons in chiral symmetry breaking, we explore their properti... more To elucidate the role played by instantons in chiral symmetry breaking, we explore their properties, in full QCD, around the critical temperature. We study in particular spatial correlations between low-lying Dirac eigenmodes and instantons. Our measurements are compared with the predictions of instanton-based models.
Nuclear Physics B - Proceedings Supplements, 1993
We measure the sweep-to-sweep autocorrelations of blocked loops below and above the deconfinement... more We measure the sweep-to-sweep autocorrelations of blocked loops below and above the deconfinement transition for SU(3) on a 16 4 lattice using 20000-140000 Monte-Carlo updating sweeps. A divergence of the autocorrelation time toward the critical β is seen at high blocking levels. The peak is near β = 6.33 where we observe 440 ± 210 for the autocorrelation time of 1 × 1 Wilson loop on 2 4 blocked lattice. The mixing of 7 Brown-Woch overrelaxation steps followed by one pseudo-heat-bath step appears optimal to reduce the autocorrelation time below the critical β. Above the critical β, however, no clear difference between these two algorithms can be seen and the system decorrelates rather fast.
Journal of High Energy Physics, 2003
We study charmonium using the standard relativistic formalism in the quenched approximation, on a... more We study charmonium using the standard relativistic formalism in the quenched approximation, on a set of lattices with isotropic lattice spacings ranging from 0.1 to 0.04 fm. We concentrate on the calculation of the hyperfine splitting between η c and J/ψ, aiming for a controlled continuum extrapolation of this quantity. The splitting extracted from the non-perturbatively improved clover Dirac operator shows very little dependence on the lattice spacing for a ≤ 0.1fm. The dependence is much stronger for Wilson and tree-level improved clover operators, but they still yield consistent extrapolations if sufficiently fine lattices, a ≤ 0.07 fm (aM(η c ) ≤ 1), are used. Our result for the hyperfine splitting is 77(2)(6) MeV (where Sommer's parameter, r 0 , is used to fix the scale). This value remains about 30% below experiment. Dynamical fermions and OZI-forbidden diagrams both contribute to the remainder. Results for the η c and J/ψ wave functions are also presented.
Progress of Theoretical Physics Supplement, 1996
We present the Japanese-European QCD-TARO collaboration. We discuss the hardware basis and the co... more We present the Japanese-European QCD-TARO collaboration. We discuss the hardware basis and the concept of analyses and present selected results. We comment on the chances and bottlenecks connected to the non-local, international character of the collaboration.
Physics Letters B, 2005
The properties of hadron screening masses around the deconfinement phase transition at finite bar... more The properties of hadron screening masses around the deconfinement phase transition at finite baryonic density can be studied by evaluating the Taylor coefficients with respect to the iso-scalar (µS = µu = µ d ) and iso-vector (µV = µu = −µ d ) chemical potentials, where µu and µ d are u and d quark chemical potentials. We simulate 2-flavour lattice QCD with staggered fermions on a 12 2 × 24 × 6 lattice with ma = 0.05 and 0.10 and report investigations of nucleon, pseudo-scalar and vector mesons. We present new, strong evidence that in the confining phase, the screening masses at µ = 0 have significant temperature dependence, but the effect of µS is very small. Above the critical temperature, the second derivative terms of mesons rapidly increase as contrasted to the case of baryon. We also study the responses of the screening masses to an iso-vector chemical potential and discuss some of the issues related to the properties of hadron masses at finite µ.
Nuclear Physics B - Proceedings Supplements, 1994
ABSTRACT We briefly summarize our results of quenched Wilson hadron spectroscopy at β = 6.3 on a ... more ABSTRACT We briefly summarize our results of quenched Wilson hadron spectroscopy at β = 6.3 on a 323 × 48 lattice. The spectrum of pseudo scalar and vector mesons, (1/2)+ and (3/2)+ baryons composed of up, down, strange and charm quarks are presented. A decrease of mass splitting between (1/2)+ and (3/2)+ baryons is observed when heavy quark masses increase, as in the case of the mass difference between pseudo scalar and vector masses.
Nuclear Physics B - Proceedings Supplements, 1993
Quenched Wilson hadron spectroscopy at fl = 6.3 has been studied by using parallel computer AP100... more Quenched Wilson hadron spectroscopy at fl = 6.3 has been studied by using parallel computer AP1000. Spectrum of hadrons composed of various combinations of hopping parameters are measured on 32 s × 48 and 163 )<48 lattices. We report results of spatial size effects based on various hadron masses. Dependence on boundary conditions along the temporal direction is also examined and discussed.
Journal of Physics A: Mathematical and General, 1988
We study by Monte Carlo simulations, using two different algorithms, the Edwards walk in two dime... more We study by Monte Carlo simulations, using two different algorithms, the Edwards walk in two dimensions and extract its critical exponents. We establish that the fractal dimension computed in terms of critical exponents is different from the HausdorR dimension computed by measure-theoretic methods.
Nuclear Physics B- …, 1999
To elucidate the role played by instantons in chiral symmetry breaking, we explore their properti... more To elucidate the role played by instantons in chiral symmetry breaking, we explore their properties, in full QCD, around the critical temperature. We study in particular spatial correlations between low-lying Dirac eigenmodes and instantons. Our measurements are compared with the predictions of instanton-based models.
Nuclear Physics B - Proceedings Supplements, 1993
We measure the sweep-to-sweep autocorrelations of blocked loops below and above the deconfinement... more We measure the sweep-to-sweep autocorrelations of blocked loops below and above the deconfinement transition for SU(3) on a 16 4 lattice using 20000-140000 Monte-Carlo updating sweeps. A divergence of the autocorrelation time toward the critical β is seen at high blocking levels. The peak is near β = 6.33 where we observe 440 ± 210 for the autocorrelation time of 1 × 1 Wilson loop on 2 4 blocked lattice. The mixing of 7 Brown-Woch overrelaxation steps followed by one pseudo-heat-bath step appears optimal to reduce the autocorrelation time below the critical β. Above the critical β, however, no clear difference between these two algorithms can be seen and the system decorrelates rather fast.