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Light hadron spectroscopy with O(a) improved dynamical fermions

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 Added by Hartmut Wittig
 Publication date 1998
  fields
and research's language is English




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We present the first results for the static quark potential and the light hadron spectrum using dynamical fermions at $beta=5.2$ using an O(a) improved Wilson fermion action together with the standard Wilson plaquette action for the gauge part. Sea quark masses were chosen such that the pseudoscalar-vector mass ratio, m_PS/m_V$, varies from 0.86 to 0.67. Finite-size effects are studied by using three different volumes, 8^3cdot 24, 12^3cdot 24 and 16^3cdot 24. Comparing our results to previous ones obtained using the quenched approximation, we find evidence for sea quark effects in quantities like the static quark potential and the vector-pseudoscalar hyperfine splitting.



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We simulate two dynamical, mass degenerate light quarks on 16^3x32 lattices with a spatial extent of 2.4 fm using the Chirally Improved Dirac operator. The simulation method, the implementation of the action and signals of equilibration are discussed in detail. Based on the eigenvalues of the Dirac operator we discuss some qualitative features of our approach. Results for ground state masses of pseudoscalar and vector mesons as well as for the nucleon and delta baryons are presented.
We present a high statistics study of the light hadron spectrum and quark masses in QCD with two flavors of dynamical quarks. Numerical simulations are carried out using the plaquette gauge action and the O(a)-improved Wilson quark action at beta=5.2, where the lattice spacing is found to be a=0.0887(11)fm from rho meson mass, on a 20^3times 48 lattice. At each of five sea quark masses corresponding to m_{PS}/m_{V} simeq 0.8-0.6, we generate 12000 trajectories using the symmetrically preconditioned Hybrid Monte Carlo algorithm. Finite spatial volume effects are investigated employing 12^3 times 48, 16^3 times 48 lattices. We also perform a set of simulations in quenched QCD with the same lattice actions at a similar lattice spacing to those for the full QCD runs. In the meson sector we find clear evidence of sea quark effects. The J parameter increases for lighter sea quark masses, and the full QCD meson masses are systematically closer to experiment than in quenched QCD. Careful finite-size studies are made to ascertain that these are not due to finite-size effects. Evidence of sea quark effects is less clear in the baryon sector due to larger finite-size effects. We also calculate light quark masses and find m_{ud}^{MS}(2GeV) =3.223(+0.046/-0.069)MeV and m_s^{MS}(2GeV)=84.5(+12.0/-1.7)MeV which are about 20% smaller than in quenched QCD.
We report on our study of light hadron spectrum and quark masses in QCD with two flavors of dynamical quarks. Simulations are made with the plaquette gauge action and the non-perturbatively $O(a)$ improved Wilson quark action. We simulate 5 sea qaurk masses corresponding to $m_{PS}/m_{V} simeq 0.8$--0.6 at $beta=5.2$ on $12^3 times 48$, $16^3 times 48$ and $20^3 times 48$ lattices. A comparison with previous calculations in quenched QCD indicates sea quark effects in meson and quark masses.
We present results on light hadron masses from simulations of full QCD and report on experiences in running such simulations on a Hitachi SR8000-F1 supercomputer.
We present preliminary results for the light harden spectrum in $N_f=2+1$ lattice QCD obtained with the nonperturbatively $O(a)$-improved Wilson quark action and the Iwasaki gauge action. Simulations are carried out at $beta=1.90$ on a $32^3 times 64$ lattice using the PACS-CS computer. We employ Luschers domain-decomposed HMC algorithm to reduce the up-down quark masses toward the physical value. The pseudoscalar meson masses range from 730 MeV down to 210 MeV. We compare the light harden spectrum extrapolated to the physical point with the experimental values.
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