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Register a new userHadron spectroscopy and static quark potential in full QCD: A comparison of improved actions on the CP-PACS
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We present first results from a full QCD calculation on the CP-PACS, comparing various actions at $a^{-1} sim 1 GeV$ and $m_pi/m_rho approx 0.7$--0.9. We use the plaquette and a renormalization group improved action for the gluons, and the Wilson and the SW-Clover action for quarks. We find that significant improvements in the hadron spectrum results from improving the quarks, while the gluon improvement is required for a rotationally invariant static potential. An ongoing effort towards exploring the chiral limit in full QCD is described.
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We investigate effects of action improvement on the light hadron spectrum and the static quark potential in two-flavor QCD for $a^{-1} approx 1$ GeV and $m_{PS}/m_V = 0.7-0.9$. We compare a renormalization group improved action with the plaquette action for gluons, and the SW-clover action with the Wilson action for quarks. We find a significant improvement in the hadron spectrum by improving the quark action, while the gluon improvement is crucial for a rotationally invariant static potential. We also explore the region of light quark masses corresponding to $m_{PS}/m_V geq 0.4$ on a 2.7 fm lattice using the improved gauge and quark action. A flattening of the potential is not observed up to 2 fm.
We report results on the static quark potential in two-flavor full QCD. The calculation is performed for three values of lattice spacing $a^{-1}approx 0.9, 1.3$ and 2.5 GeV on $12^3{times}24, 16^3{times}32$ and $24^3{times}48$ lattices respectively, at sea quark masses corresponding to $m_pi/m_rho approx 0.8-0.6$. An RG-improved gauge action and a tadpole-improved SW clover quark action are employed. We discuss scaling of $m_{rho}/sqrt{sigma}$ and effects of dynamical quarks on the potential.
We present the final results of the CP-PACS calculation of the light hadron spectrum and quark masses with two flavors of dynamical quarks. Simulations are made with a renormalization-group improved gauge action and a mean-field improved clover quark action for sea quark masses corresponding to $m_{rm PS}/m_{rm V} approx 0.8$--0.6 and the lattice spacing $a=0.22$--0.11 fm. For the meson spectrum in the continuum limit a clearly improved agreement with experiment is observed compared to the quenched case, demonstrating the importance of sea quark effects. For light quark masses we obtain $m_{ud}^{bar{MS}}(2GeV)=3.44^{+0.14}_{-0.22}$ MeV and $m_s^{bar{MS}}(2GeV)=88^{+4}_{-6}$ MeV ($K$-input) and $m_s^{bar{MS}}(2GeV)=90^{+5}_{-11}$ MeV ($phi$-input), which are reduced by about 25% compared to the values in quenched QCD.
CP-PACS and JLQCD Collaborations are carrying out a joint project of the 2+1 flavor full QCD with the RG-improved gauge action and the non-perturbatively ${cal O}(a)$-improved Wilson quark action. This simulation removes quenching effects of all three light quarks, which is the last major uncertainty in lattice QCD. In this report we present our results for the light meson spectrum and quark masses on a $20^3times 40$ lattice at the lattice spacing $asimeq 0.10$ fm.
The quenched hadron spectrum in the continuum obtained with the Wilson quark action in recent simulations on the CP-PACS is presented. Results for the light quark masses and the QCD scale parameter are reported.
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