S. Aoki

ρ meson decay in 2+1 flavor lattice QCD

(PACS-CS Collaboration) 1 Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan 2 Center for Computational Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan 3 Department of Physics, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan 4 RIKEN Advanced Institute for Computational Science, Kobe, Hyogo 650-0047, Japan 5 Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya, Aichi 464-8602, Japan (Dated: November 28, 2011)

Nucleon strange quark content from two-flavor lattice QCD with exact chiral symmetry

Strange quark content of the nucleon is calculated in dynamical lattice QCD employing the overlap fermion formulation. For this quantity, exact chiral symmetry guaranteed by the Ginsparg-Wilson relation is crucial to avoid large contamination due to a possible operator mixing with

Charm quark system at the physical point of 2+1 flavor lattice QCD

bar{u}u+bar{d}d

Charmed baryons at the physical point in 2+1 flavor lattice QCD

. Gauge configurations are generated with two dynamical flavors on a 16^3 x 32 lattice at a lattice spacing a simeq 0.12fm. We directly calculate the relevant three-point function on the lattice including a disconnected strange quark loop utilizing the techniques of all-to-all quark propagator and low-mode averaging. Our result f_{T_s} = 0.032(8)(22), is in good agreement with our previous indirect estimate using the Feynman-Hellmann theorem.

Phase structure of finite temperature QCD in the heavy quark region

1 Center for Computational Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan 2 Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan 3 Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan 4 Riken BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973, USA 5 RIKEN Advanced Institute for Computational Science, Kobe, Hyogo 650-0047, Japan (Dated: January 20, 2013)

Charmonium spectral functions with the variational method in zero and finite temperature lattice QCD

We investigate the charmed baryon mass spectrum using the relativistic heavy quark action on 2+1 flavor PACS-CS configurations previously generated on 32 3 × 64 lattice. The dynamical updown and strange quark masses are tuned to their physical values, reweighted from those employed in the configuration generation. At the physical point, the inverse lattice spacing determined from the baryon mass gives a 1 = 2.194(10) GeV, and thus the spatial extent becomes L = 32a = 2.88(1) fm. Our results for the charmed baryon masses are consistent with experimental values, �

η′meson mass from topological charge density correlator in QCD

We study the quark mass dependence of the finite temperature QCD phase transition in the heavy quark region using an effective potential defined through the probability distribution function of the average plaquette. Performing a simulation of SU(3) pure gauge theory, we first confirm that the distribution function has two peaks indicating that the phase transition is of first order in the heavy quark limit, while the first order transition turns into a crossover as the quark mass decreases from infinity, where the mass dependence of the distribution function is evaluated by the reweighting method combined with the hopping parameter expansion. We determine the endpoint of the first order transition region for Nf = 1, 2, 3 and 2 + 1 cases. The quark mass dependence of the latent heat is also evaluated in the first order transition region.

Evidence of effective axial U(1) symmetry restoration at high temperature QCD

We propose a method to evaluate spectral functions on the lattice based on a variational method. On a lattice with a finite spatial extent, spectral functions consist of discrete spectra only. Adopting a variational method, we calculate the locations and the heights of spectral functions at low-lying discrete spectra. We first test the method in the case of analytically solvable free Wilson quarks at zero and finite temperatures and confirm that the method well reproduces the analytic results for low-lying spectra. We find that we can systematically improve the results by increasing the number of trial states. We then apply the method to calculate the charmonium spectral functions for S and P-wave states at zero-temperature in quenched QCD and compare the results with those obtained using the conventional maximum entropy method (MEM). The results for the ground state are consistent with the location and the area of the first peak in spectral functions from the MEM, while the variational method leads to a mass which is closer to the experimental value for the first excited state. We also investigate the temperature dependence of the spectral functions for S-wave states below and above T{sub c}. We obtain no clear evidences formorexa0» dissociation of J/{psi} and {eta}{sub c} up to 1.4T{sub c}.«xa0less

Histograms in heavy-quark QCD at finite temperature and density

The flavor-singlet component of the eta prime meson is related to the topological structure of the SU(3) gauge field through the chiral anomaly. We perform a 2+1-flavor lattice QCD calculation and demonstrate that the two-point function of a gluonically defined topological charge density after a short Yang-Mills gradient flow contains the propagation of the eta prime meson, by showing that its mass in the chiral and continuum limit is consistent with the experimental value. The gluonic correlator does not suffer from the contamination of the pion contribution, and the clean signal is obtained at significantly lower numerical cost compared to the conventional method with the quark bilinear operators.

Kaon-Nucleon potential from lattice QCD

We study the axial U(1) symmetry at a finite temperature in two-flavor lattice QCD. Employing the Mobius domain-wall fermions, we generate gauge configurations slightly above the critical temperature Tc with different lattice sizes L=2–4u2009u2009fm. Our action allows frequent topology tunneling while keeping good chiral symmetry close enough to that of overlap fermions. This allows us to recover full chiral symmetry by an overlap/domain-wall reweighting. Above the phase transition, a strong suppression of the low-lying modes is observed in both overlap and domain-wall Dirac spectra. We, however, find a sizable violation of the Ginsparg-Wilson relation in the Mobius domain-wall Dirac eigenmodes, which dominates the signals of the axial U(1) symmetry breaking near the chiral limit. We also find that the use of the overlap fermion only in the valence sector is dangerous since it suffers from the artifacts due to partial quenching. Reweighting the Mobius domain-wall fermion determinant to that of the overlap fermion, we observe the axial U(1) breaking to vanish in the chiral limit, which is stable against the changes of the lattice volume and lattice spacing.