Search

We report results of quark masses in quenched lattice QCD with the Kogut-Susskind fermion action, employing the Reguralization Independent scheme (RI) of Martinelli et al. to non-perturbatively evaluate the renormalization factor relating the bare quark mass on the lattice to that in the continuum. Calculations are carried out at \beta=6.0, 6.2, and 6.4, from which we find $m^{\bar{MS}}_{ud} (2 GeV)= 4.23(29) MeV$ for the average up and down quark mass and, with the $\phi$ meson mass as input, $m^{\bar{MS}}_{s} (2 GeV)= 129(12) MeV$ for the strange mass in the continuum limit. These values are about 20% larger than those obtained with the one-loop perturbative renormalization factor., Comment: LaTeX, 11 pages, 4 eps figures, uses revtex and epsf

A lattice QCD calculation of the kaon $B$ parameter $B_K$ is carried out with the Wilson quark action in the quenched approximation at $\beta=6/g^2=5.9-6.5$. The mixing problem of the $\Delta s=2$ four-quark operators is solved non-perturbatively with full use of chiral Ward identities employing four external quarks with an equal off-shell momentum in the Landau gauge. This method, without invoking any effective theory, enables us to construct the weak four-quark operators exhibiting good chiral behavior. Our results for $B_K$ with the non-perturbative mixing coefficients show small scaling violation beyond the lattice cut-off $a^{-1}\sim 2.5 $GeV. Our estimate concludes $B_K(NDR, 2 GeV)=0.69(7)$ at $a^{-1}=2.7-4.3$GeV, which agrees with the value obtained with the Kogut-Susskind quark action. For comparison we also calculate $B_K$ with one-loop perturbative mixing coefficients. While this yields incorrect values at finite lattice spacing, a linear extrapolation to the continuum limit as a function of $a$ leads to a result consistent with those obtained with the Ward identity method., Comment: 42 pages, 22 Postscript figures, added a new reference[26]

We report on a study of heavy hybrid states using the NRQCD approach on coarse and asymmetric lattices, where we discard vacuum polarisation effects and neglect all spin-correction terms. We find a clear hybrid signal on all our lattices ($a_s= 0.15 ... 0.47$ fm). We have studied in detail the lattice spacing artefacts, finite volume effects and mass dependence. Within the above approximations we predict the hybrid excitation in Charmonium to be 1.323(13) GeV above its ground state. The bottomonium hybrid was found to be 1.542(8) GeV above its ground state., Comment: 7 pages, Latex, 3 figures

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., Comment: LATTICE98(spectrum), 3 pages, 4 figures

We report preliminary results of our study of matrix elements of baryon number violating operators which appear in the low-energy effective Lagrangian of (SUSY-)Grand Unified Theories. The calculation is performed on a $32^{3}\times80$ lattice at $\beta=6.1$ using Wilson fermions in the quenched approximation. Our calculation is independent of details of (SUSY-)GUT models and covers all interesting decay modes., Comment: LATTICE98(matrixelements), 3 pages, 3 figures

We investigate the scaling behavior of the $B$ meson decay constant $f_B$ and $f_{B_{s}}$ at $\beta$$=$$5.7, 5.9, 6.1$, employing the NRQCD heavy quark action and the clover light quark action. Mixing effect from dimension-4 operator in the heavy-light axial-vector current is studied, and we find that the $a$ dependence of $f_B$ is significantly reduced. Our preliminary result for the decay constants in the quenched approximation is $f_{B}$$=$$162(^{+35}_{-18})$ MeV, $f_{B_{s}}$$=$$190(^{+40}_{-19})$ MeV, and $f_{B_{s}}/f_{B}$$=$$1.18(^{+6}_{-6})$., Comment: LATTICE98(matrixelement), 3 pages, 3 eps figures

We report the final results of the CP-PACS calculation for the quenched light hadron spectrum with the Wilson quark action. Our data support the presence of quenched chiral singularities, and this motivates us to use mass formulae based on quenched chiral perturbation theory in order to extrapolate hadron masses to the physical point. Hadron masses and decay constants in the continuum limit show unambiguous systematic deviations from experiment. We also report the results for light quark masses., Comment: LATTICE98(spectrum). The poster at Lattice98 can be obtained from http://www.rccp.tsukuba.ac.jp/people/yoshie/Lat98.Poster/

Light quark masses are computed for Kogut-Susskind fermions by evaluating non-perturbatively the renormalization factor for bilinear quark operators. Calculations are carried out in the quenched approximation at \beta=6.0, 6.2, and 6.4. For the average up and down quark mass we find $m_{\bar MS}(2 GeV)= 4.15(27) MeV$ in the continuum limit, which is significantly larger than $3.51(20) MeV$ ($q^*=1/a$) or $3.40(21) MeV$ ($q^*=\pi/a$) obtained with the one-loop perturbative renormalization factor., Comment: LATTICE98(matrixelement), 3 pages, 4 eps figures

We report on an on-going two-flavor full QCD study on CP-PACS using an RG-improved gauge action and a tadpole-improved SW quark action. Runs are made for three lattice spacings $a^{-1}\approx 0.9$, 1.3, and 2.5 GeV on $12^3\times24$, $16^3\times32$, and $24^3\times48$ lattices. Four sea quark masses having $m_{\rm PS}/m_{\rm V} \approx 0.8$--0.6 are simulated, for each of which hadron masses are evaluated for valence quark masses corresponding to $m_{\rm PS}/m_{\rm V} \approx 0.8$--0.5. Results for hadron and light quark masses are presented and compared with those obtained in quenched QCD., Comment: LATTICE98(spectrum), 3 pages, 3 figures

We report on a study of the finite-temperature chiral transition on an $N_t=4$ lattice for 2+1 flavors of Kogut-Susskind quarks. We find the point of physical quark masses to lie in the region of crossover, in agreement with results of previous studies. Results of a detailed examination of the $m_{u,d}=m_s$ case indicate vanishing of the screening mass of $\sigma$ meson at the end point of the first-order transition., Comment: LATTICE98(hightemp), 3 pages, 4 figures

We investigate the phase structure of lattice QCD for general number of flavors $N_F$. Based on numerical data combined with the results of the perturbation theory we propose the following picture: When $N_F \ge 17$, there is only one IR fixed point at vanishing gauge coupling, i.e., the theory in the continuum limit is trivial. On the other hand, when $16 \ge N_F \ge 7$, there is a non-trivial fixed point. Therefore, the theory is non-trivial with anomalous dimensions, however, without quark confinement. Theories which satisfy both quark confinement and spontaneous chiral symmetry breaking in the continuum limit exist only for $N_F \le 6$., Comment: Talk presented by K. Kanaya at the 1997 Yukawa International Seminar (YKIS'97) on ``Non-Perturbative QCD --- Structure of the QCD Vacuum ---'', YITP, Kyoto, Japan, 2--12 Dec. 1997. To be published in the proceedings [Prog. Theor. Phys. Suppl.]

We present a calculation for the $K^+\to\pi^+ \pi^0 $ decay amplitude using a quenched simulation of lattice QCD with the Wilson quark action at $\beta=6/g^2=6.1$. The decay amplitude is extracted from the ratio, the $K\to\pi\pi$ three-point function divided by either $K$ and $\pi$ meson two-point functions or $K$ meson two-point function and I=2 $\pi\pi$ four-point function; the two different methods yield consistent results. Finite size effects are examined with calculations made on $24^3\times 64$ and $32^3\times 64$ lattices, and are shown that they are explained by one-loop effects of chiral perturbation theory. The lattice amplitude is converted to the continuum value by employing a one-loop calculation of chiral perturbation theory, yielding a value in agreement with experiment if extrapolated to the chiral limit. We also report on the $K$ meson $B$ parameter $B_K$ obtained from the $K^+\to\pi^+\pi^0$ amplitude using chiral perturbation theory., Comment: LaTeX, 23 pages, 8 figures, uses revtex and epsf

A lattice QCD calculation of the B meson decay constant is presented. In order to investigate the scaling violation associated with the heavy quark, parallel simulations are carried out employing both Wilson and the O(a)-improved clover actions for the heavy quark. The discretization errors due to the large $b$ quark mass are estimated in a systematic way with the aid of the non-relativistic interpretation approach of El-Khadra, Kronfeld and Mackenzie. As our best value from the quenched simulations at $\beta$=5.9, 6.1 and 6.3 we obtain $f_B$=163$\pm$16 MeV and $f_{B_s}$=175$\pm$18 MeV in the continuum limit where the error includes both statistical and systematic uncertainties., Comment: 10 pages, 4 figures

We present results of our quenched study of the B meson decay constant obtained with a parallel set of simulations with the Wilson and Clover actions at \beta=5.9, 6.1 and 6.3. Systematic errors associated with the large b-quark mass are analyzed within the Fermilab non-relativistic formalism. As our best estimate in the continuum limit we obtain $f_B=163 \pm 16 MeV$ and $f_{B_s}=175 \pm 18 MeV$ with the Clover action., Comment: 3 pages, 3 figures, talk presented by S. Hashimoto at LATTICE97, Edinburgh, 22-26 July 1997

We present our study of the dependence of the heavy-to-light semileptonic B decay form factors on the heavy-light meson mass $M_{PS}$. Simulations are made over a range of the heavy quark mass covering both the charm and bottom quarks using the $O(a)$-improved clover action at $\beta=5.9$ on a $16^3\times 40$ and $24^3\times 64$ lattice. We find that a weak dependence of form factors on $M_{PS}$ observed in previous studies in the region of charm quark persists up to the region of$b$ quark. The soft pion relation $f^0(q^2_{max})=f_B/f_\pi$ is examined and found to be largely violated., Comment: 3 pages, latex source-file, 4 figures as epsf-file, uses espcrc2.sty. Talk presented by S. Tominaga at Lattice 97, Edinburgh, Scotland, 22-26 Jul 1997

Recent developments in calculations of the light hadron spectrum are reviewed. Particular emphasis is placed on discussion of to what extent the quenched spectrum agrees with experiment. Recent progress, both for quenched and full QCD, in reducing scaling violation with the use of improved actions is presented., Comment: Plenary talk presented at Lattice 97, 13 pages, LaTeX (espcrc2,epsf), 14 ps figures

We present results for the light quark masses for the Wilson quark action obtained with the PCAC relation for the one-link extended axial vector current in quenched QCD at $\beta=5.9-6.5$. This method leads to a remarkable improvement of scaling behavior of the light quark masses compared to the conventional method. We obtain ${\bar m}_l=3.87(37)$MeV for the averaged up and down quark mass and ${\bar m}_s=97(9)$MeV for the strange quark mass in the ${\barMS}$ scheme at $\mu=2$GeV., Comment: 3 pages, latex source-file, 2 figures as epsf-file, uses espcrc2.sty. Poster presented at Lattice 97: 15th International Symposium on Lattice Field Theory, Edinburgh, Scotland, 22-26 Jul 1997

We present a detailed description of the method and results of our calculation of the kaon B parameter using the Wilson quark action in quenched QCD at $\beta=5.9-6.5$. The mixing problem of the $\Delta s=2$ four-quark operators is solved non-perturbatively with full use of chiral Ward identities. We find $B_K(NDR, 2 GeV)=0.562(64)$ in the continuum limit, which agrees with the value obtained with the Kogut-Susskind quark action., Comment: 10 pages, latex source-file, 10 figures as epsf-file, uses espcrc2.sty. Talk given at International Workshop on Lattice QCD on Parallel Computers, 10-15 Mar 1997, Tsukuba, Japan

A new study is reported of a lattice QCD calculation of the $K^+\to\pi^+ \pi^0 $ decay amplitude with the Wilson quark action in the quenched approximation at $\beta=6.1$. The amplitude is extracted from the $K\to\pi\pi$ Green function, and a conversion to the continuum value is made employing a recent one-loop calculation of chiral perturbation theory. The result is consistent with the experimental value if extrapolated to the chiral limit., Comment: LaTeX, 3 pages, 3 figures, uses espcrc2 and epsfig. Talk presented at Lattice '97, Edinburgh, Scotland, July 1997

We present results of a large-scale simulation for the Kaon B parameter $B_K$ in quenched lattice QCD with the Kogut-Susskind quark action. Calculating $B_K$ at 1% statistical accuracy for seven values of lattice spacing in the range $a\approx 0.24-0.04$ fm on lattices up to $56^3\times 96$, we verify a quadratic $a$ dependence of $B_K$ theoretically predicted. Strong indications are found that, with our level of accuracy, $\alpha_{\bar{MS}}(1/a)^2$ terms arising from our one-loop matching procedure have to be included in the continuum extrapolation. We present $B_K$(NDR, 2 GeV)=0.628(42) as our final value, as obtained by a fit including the $\alpha_{\bar{MS}}(1/a)^2$ term., Comment: 8 pages, Latex(revtex, epsf), 2 epsf figures

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., Comment: 6 pages, based on talks presented by R. Burkhalter and T. Kaneko at Lattice97, Edinburgh

We present progress report of a CP-PACS calculation of quenched QCD spectrum with the Wilson quark action. Light hadron masses and meson decay constants are obtained at $\beta=$5.9, 6.1, and 6.25 on lattices with a physical extent of 3 fm, and for the range of quark mass corresponding to $m_\pi/m_\rho \approx 0.75$ $-$ 0.4. Nucleon mass at each $\beta$ appears to be a convex function of quark mass, and consequently the value at the physical quark mass is much smaller than previously thought. Hadron masses extrapolated to the continuum limit exhibits a significant deviation from experimental values: with $K$ meson mass to fix strange quark mass, strange meson and baryon masses are systematically lower. Light quark masses determined from the axial Ward identity are shown to agree with those from perturbation theory in the continuum limit. Decay constants of mesons are also discussed., Comment: 12 pages, Latex(espcrc2,epsf), 17 ps figures. Talk presented by T.Yoshi\'e at the International Workshop on ``LATTICE QCD ON PARALLEL COMPUTERS'', 10-15 March 1997, Center for Computational Physics, University of Tsukuba

We report on a study of two-flavor finite-temperature chiral phase transition employing the Kogut-Susskind quark action and the plaquette gluon action in lattice QCD for a lattice with $N_t=4$ temporal size. Hybrid R simulations of $10^4$ trajectories are made at quark masses of $m_q=0.075, 0.0375, 0.02, 0.01$ in lattice units for the spatial sizes $8^3, 12^3$ and $16^3$. The spatial size dependence of various susceptibilities confirm the previous conclusion of the absence of a phase transition down to $m_q=0.02$. At $m_q=0.01$ an increase of susceptibilities is observed up to the largest volume $16^3$ explored in the present work. We argue, however, that this increase is likely to be due to an artifact of too small a lattice size and it cannot be taken to be the evidence for a first-order transition. Analysis of critical exponents estimated from the quark mass dependence of susceptibilities shows that they satisfy hyperscaling consistent with a second-order transition located at $m_q=0$. The exponents obtained from larger lattice, however, deviate significantly from both those of O(2), which is the exact symmetry group of the Kogut-Susskind action at finite lattice spacing, and those of O(4) expected from an effective sigma model analysis in the continuum limit., Comment: 29 pages, Latex(epsf), 11 ps figures

A summary is presented of a scaling study of the finite-temperature chiral phase transition of two-flavor QCD with the Kogut-Susskind quark action based on simulations on $L^3\times4$ ($L$=8, 12 and 16) lattices at the quark mass of $m_q=0.075, 0.0375, 0.02$ and 0.01. We find a phase transition to be absent for $m_q\geq 0.02$, and also quite likely at $m_q=0.01$. The quark mass dependence of susceptibilities is consistent with a second-order transition at $m_q=0$. The exponents, however, deviate from the O(2) and O(4) values theoretically expected., Comment: 3 pages, Latex(espcrc2,epsf), 3 ps figures, Poster presented at Lattice 97

We investigate the finite-temperature phase structure and the scaling of the chiral condensate in lattice QCD with two degenerate light quarks, using a renormalization group improved gauge action and the Wilson quark action. We obtain a phase diagram which is consistent with that from the parity-flavor breaking scenario. The scaling relation for the chiral condensate assuming the critical exponents and the scaling function of the three dimensional O(4) model is remarkably satisfied for a wide range of parameters. This indicates that the chiral transition in two flavor QCD is of second order in the continuum limit., Comment: LaTeX, 3 pages, 4 EPS figures, Talk presented at LATTICE97 (finite temperature)

A report is presented on our continued effort to elucidate the continuum limit of $B_K$ using the quenched Kogut-Susskind quark action. By adding to our previous simulations one more point at $\beta = 6.65$ employing a $56^3\times 96$ lattice, we now confirm the expected $O(a^2)$ behavior of $B_K$ with the Kogut-Susskind action. A simple continuum extrapolation quadratic in $a$ leads to $B_K$(NDR, 2 GeV) = 0.598(5). As our final value of $B_K$ in the continuum we present $B_K$(NDR, 2 GeV)=0.628(42), as obtained by a fit including an $\alpha_{\bar{MS}}(1/a)^2$ term arising from the lattice-continuum matching with the one-loop renormalization., Comment: 3 pages, Latex(espcrc2,epsf), 2 ps figures, Talk presented at Lattice 97, two important references added

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., Comment: Talk presented by K. Kanaya at Lattice97, Edinburgh

A status report is made of an on-going full QCD study on the CP-PACS aiming at a comparative analysis of the effects of improving gauge and quark actions on hadronic quantities and static quark potential. Simulations are made for four action combinations, the plaquette or an RG-improved action for gluons and the Wilson or SW-clover action for quarks, at $a^{-1} \approx 1.1$-1.3GeV and $m_\pi/m_\rho \approx 0.7$-0.9. Results demonstrate clearly that the clover term markedly reduces discretization errors for hadron spectrum, while adding six-link terms to the plaquette action leads to much better rotational symmetry in the potential. These results extend experience with quenched simulations to full QCD., Comment: Talk presented by K. Kanaya at the International Workshop on ``LATTICE QCD ON PARALLEL COMPUTERS'', 10-15 March 1997, Center for Computational Physics, University of Tsukuba

Report is made of a systematic scaling study of the finite-temperature chiral phase transition of two-flavor QCD with the Kogut-Susskind quark action based on simulations on $L^3\times4$ ($L$=8, 12 and 16) lattices at the quark mass of $m_q=0.075, 0.0375, 0.02$ and 0.01. Our finite-size data show that a phase transition is absent for $m_q\geq 0.02$, and quite likely also at $m_q=0.01$. The scaling behavior of susceptibilities as a function of $m_q$ is consistent with a second-order transition at $m_q=0$. However, the exponents deviate from the O(2) or O(4) values theoretically expected., Comment: Talk presented by M. Okawa at the International Workshop on `` LATTICE QCD ON PARALLEL COMPUTERS", 10-15 March 1997, Center for Computational Physics, University of Tsukuba. 7 LaTeX pages plus 5 postscript figures, uses espcrc2.sty

The kaon B parameter is calculated in quenched lattice QCD with the Wilson quark action. The mixing problem of the \Delta s=2 four-quark operators is solved non-perturbatively with full use of chiral Ward identities, and this method enables us to construct the weak four-quark operators exhibiting good chiral behavior. We find B_K(NDR, 2GeV)=0.562(64) in the continuum limit, which agrees with the value obtained with the Kogut-Susskind quark action., Comment: 11 pages, latex source-file, 4 figures as ps-file

We study the scaling properties of the static quark potential and the ratio of the critical temperature $T_c$ to the square root of the string tension $\sigma$ in the SU(3) pure gauge theory using a renormalization group improved action. We first determine the critical coupling $\beta_c$ on lattices with temporal extension $N_t=3$, 4, and 6, and then calculate the static quark potential at the critical couplings on lattices at zero temperature. We note that the static quark potentials obtained are rotationally invariant with errors of at most 1 - 2 % in all the three cases, and that the potential $V(R)$ in physical units scales in the whole region of $R$ investigated. The values of $T_{c}/\sqrt{\sigma}$ for the three cases in the infinite volume limit are identical within errors. We estimate the value in the continuum limit to be $T_{c}/\sqrt{\sigma} = 0.656(4)$, which is slightly larger than the value in the continuum limit from the one-plaquette action, 0.629(3)., Comment: 32 pages of Latex, 13 PostScript figures. Replaced version containing extended finite size scaling analyses on $15^{3}\times3$ and $20^{3}\times4$ lattices

The finite temperature transition of QCD with two degenerate light quarks is studied on the lattice with a renormalization group improved gauge action and the Wilson quark action. We have made simulations on an $8^3\times 4$ lattice near the chiral transition point. It is shown that the chiral condensate which is the order parameter of chiral symmetry satisfies remarkably a scaling relation with the exponents of the three dimensional O(4) Heisenberg model. This indicates that the chiral transition in two-flavor QCD is of second order in the continuum limit., Comment: 13 pages, 6 figures

We propose a non-perturbative method to determine the mixing coefficients of $\Delta s=2$ four-quark operators for the Wilson quark action using chiral Ward identities. The method is applied to calculate B_K in quenched QCD., Comment: 3 pages including 3 figures, Talk presented at LATTICE96(phenomenology) by Y. Kuramashi

Several topics concerning the light hadron spectrum are discussed. Flavor symmetry breaking effects and the problem of quenched chiral logarithm are examined with pion mass data for the Kogut-Susskind quark action, and light meson decay constants for the Wilson action calculated with non-perturbative renormalization constants are discussed. Results for quark masses are also given both for the Kogut-Susskind and Wilson actions., Comment: 3 pages, latex, 5 figures, Talk presented at LATTICE96(spectrum), reference corrected

We explore the problems in calculating the decay constant for heavy-light mesons using the quenched Wilson quark action for both heavy and light quarks. We find that the continuum limit of the decay constant is reasonably converged among different prescriptions after the continuum limit is taken. A number of technical problems associated with prescriptions are also addressed., Comment: 3 pages including 5 figures, Talk presented at LATTICE96(heavy quarks) by S. Hashimoto

We present new results of our ongoing project toward a precision determination of the kaon $B$ parameter with the Kogut-Susskind quark action in quenched QCD. New results taken at $\beta$=6.4 and $\beta=5.7$ suggest that an apparently linear $a$ dependence of $B_K$ previously observed for $\beta=5.85-6.2$ arises from a change of curvature from convex to concave as the lattice spacing is reduced. Fitting data for $\beta\geq 5.93$ with an $O(a^2)$ form yields $B_K$(NDR,2 GeV)=0.587(7)(17) in the continuum limit. We also describe a finite-size study of $B_K$ at $\beta=$ 6.0 and 6.4, and a reanalysis of the theoretical argument for $O(a^2)$ behavior., Comment: 4 pages incl. 2 figures, Latex+espcrc2+epsf, Talk presented at LATTICE96(poster) by S. Aoki

We investigate and elucidate the phase structure of QCD for general number of flavors $N_F$ with Wilson quarks, varying $N_F$ from 2 up to 300. Based on numerical results combined with the result of the perturbation theory we propose the following picture: When $N_F \ge 17$, there is only a trivial fixed point and therefore the theory in the continuum limit is trivial. On the other hand, when $16 \ge N_F \ge 7$, there is a non-trivial fixed point and therefore the theory is non-trivial with anomalous dimensions, however, without quark confinement. Theories which satisfy both quark confinement and spontaneous chiral symmetry breaking in the continuum limit exist only for $N_F \le 6$. We also discuss the structure of the deconfining phase at finite temperatures for the small number of flavors such as $N_F=2$ and 3, through a systematic study of it for general number of flavors., Comment: LaTeX, 7 pages, 10 PS figures, Talk presented at LATTICE96(poster) and LATTICE96(finite temperature)

We study the scaling property of the ratio of the critical temperature $T_c$ to the square root of the string tension $\sigma$ in the SU(3) pure gauge theory using a renormalization group improved action. We first determine the critical coupling $\beta_c$ on lattices with temporal extension $N_t=4$ and 6, and then calculate the static quark potential at the critical couplings on lattices at zero temperature. The values of $T_{c}/\sqrt{\sigma}$ in the infinite volume limit are identical within errors, while they are slightly larger than the value extrapolated to the continuum limit with the standard action. We also note that the rotational invariance of the static quark potential is remarkably restored in the both cases, and that the potential $V(R)$ in physical units scales in the whole region of $R$ investigated., Comment: 3 pages of Latex, 5 PostScript figures, Talk presented at LATTICE96(finite temperature)

The nature of finite temperature transitions in lattice QCD with Wilson quarks is studied near the chiral limit for the cases of 2, 3, and 6 flavors of degenerate quarks ($N_F=2$, 3, and 6) and also for the case of massless up and down quarks and a light strange quark ($N_F=2+1$). Our simulations mainly performed on lattices with the temporal direction extension $N_t=4$ indicate that the finite temperature transition in the chiral limit (chiral transition) is continuous for $N_F=2$, while it is of first order for $N_F=3$ and 6. We find that the transition is of first order for the case of massless up and down quarks and the physical strange quark where we obtain a value of $m_\phi/m_\rho$ consistent with the physical value. We also discuss the phase structure at zero temperature as well as that at finite temperatures., Comment: uuencoded compressed tar file, 70 pages, 32 figures

We present results of a high statistics calculation of hadron masses and meson decay constants in the quenched approximation to lattice QCD with Wilson quarks at $\beta=$ 5.85 and 6.0 on $24^3 \times 54$ lattices. We analyze the data paying attention in particular to the systematic errors due to the choice of fitting range and due to the contamination from excited states. We find that the systematic errors for the hadron masses with quarks lighter than the strange quark amount to 1 --- 2 times the statistical errors. When the lattice scale is fixed from the $\rho$ meson mass, the masses of the $\Omega^{-}$ baryon and the $\phi$ meson at two $\beta$'s agree with experiment within about one standard deviation. On the other hand, the central value of the nucleon mass at $\beta=6.0$ (5.85) is larger than its experimental value by about 15\% (20\%) and that of the $\Delta$ mass by about 15\% (4\%): Even when the systematic errors are included, the baryon masses at $\beta=6.0$ do not agree with experiment. Vector meson decay constants at two values of $\beta$ agree well with each other and are consistent with experiment for a wide range of the quark mass, when we use current renormalization constants determined nonperturbatively by numerical simulations. The pion decay constant agrees with experiment albeit with large errors. Results for the masses of excited states of the $\rho$ meson and the nucleon are also presented., Comment: 50 pages, 30 figures

The CP-PACS is a massively parallel computer dedicated for calculations in computational physics and will be in operation in the spring of 1996 at Center for Computational Physics, University of Tsukuba. In this article, we describe the architecture of the CP-PACS and report the results of the estimate of the performance of the CP-PACS for typical lattice QCD calculations., Comment: 12 pages (5 figures), Postscript file, talk presented at "QCD on Massively Parallel Computers" (Yamagata, Japan, March 16-18,1995)

Finite temperature transition in lattice QCD with degenerate Wilson quarks is investigated on an $N_t=4$ lattice, using a renormalization group improved gauge action. We find the following for the $N_F=2$ case: 1) The transition is smooth for a wide range of the quark mass. 2) The chiral transition is continuous. 3) The chiral condensation well satisfies a scaling relation with the critical exponents of the 3 dimensional $O(4)$ spin model. For $N_F=3$, we find that the chiral transition is of first order., Comment: 4 pages (6 figures), Postscript file, Contribution to Lattice 95 proceedings

The nature of QCD phase transition is studied with massless up and down quarks and a light strange quark, using the Wilson formalism for quarks on a lattice with the temporal direction extension $N_t=4$. We find that the phase transition is first order in the cases of both about 150 MeV and 400 MeV for the strange quark mass. These results together with those for three degenerate quarks suggest that QCD phase transition in nature is first order., Comment: uuencoded compressed tar file, LaTeX, 13 pages, 9 figures, Minor errors for quoting references are corrected and a reference is added

The nature of the chiral phase transition in lattice QCD is studied for the cases of 2, 3 and 6 flavors with degenerate Wilson quarks, mainly on a lattice with the temporal direction extension $N_t=4$. We find that the chiral phase transition is continuous for the case of 2 flavors, while it is of first order for 3 and 6 flavors., Comment: uuencoded compressed tar file, LaTeX, 14 pages, 7 figures

The finite temperature transition or crossover in QCD with two degenerate Wilson quarks is investigated using a renormalization group improved action. At $\beta=2.0$ and 2.1 where $a^{-1} \sim 1.0-1.2$ GeV, the expectation value of the Polyakov loop and the pion screening mass on an $8^3 \times 4$ lattice vary smoothly with the hopping parameter through the transition/crossover. The quark screening mass in the high temperature phase agrees well with that in the low temperature phase calculated on an $8^4$ lattice. The smooth transition of the observables is totally different from the sharp transition found for the standard action at $\beta=5.0$ and 5.1 where $a^{-1}$ is also $1.0-1.2$ GeV., Comment: 3 pages, latex, 2 postscript figures. Contribution to Lattice 94 proceedings

The finite temperature transition in QCD is studied using Wilson quarks for the cases of $N_F=2$, 3 and 2+1. For $N_F=2$ the transition is smooth in the chiral limit on both $\nt=4$ and 6 lattices. For $N_F=3$, clear two state signals are observed for $\beta\leq4.7$ on $8^2\times10 \times4$ and $12^3\times4$ lattices, which implies the transition is first order for $m_q \simm{<} 140$ MeV. For $N_F=2+1$ we study two cases of $m_s \simeq 150$ and 400 MeV with $m_u=m_d \simeq 0$. In contrast to a previous result with staggered quarks, two state signals are clearly observed for both cases, suggesting a first order QCD phase transition in the real world., Comment: ps file, 3 pages with 4 figures

We present the results for the hadron spectrum calculated on 400 configurations using point source, wall source and 8-cubic sources, in quenched QCD with Wilson fermions at $\beta=6.0$ and $K=0.155$ on a $24^3 \times 54$ lattice. The results for the ground state masses obtained with three types of quark sources agree well with each other. Masses of the first excited states appear consistent with experimental values within large errors., Comment: 3 pages, 2 postscript figures, to appear in the Proceedings of LATTICE 93, Dallas, USA; preprint UTHEP-267

The phase structure of QCD with various number of flavors is studied for Wilson quarks. For the case of $N_F=3$ we find that the finite temperature deconfining transition is of first order in the chiral limit on an $N_t=4$ lattice. Together with our previous results that the deconfining transition in the chiral limit is continuous for $N_F=2$ and is first order for $N_F=6$, the order of the transition is found to be consistent with a prediction of universality. The case of $SU(2)$ QCD is also studied in the strong coupling limit and the phase structure is found to be quite similar to the case of $SU(3)$: There exists a critical number of flavors $N_F^*$ and for $N_F \geq N_F^*$ the confinement is broken even in the strong coupling limit for light quarks. $N_F^*=3$ corresponding to 7 for $SU(3)$., Comment: 3 pages with 5 PS figures, LaTeX (espcrc2.sty required), UTHEP-266

We calculate the tension $\sigma$ of the interface between the confined and deconfined phases by the histogram method in SU(3) lattice gauge theory for temporal extents of 4 and 6 using the recent high-statistics data by QCDPAX collaboration. The results are $\sigma/T_c^3 = 0.0292(22)$ and 0.0218(33) for $N_t=4$ and 6, respectively. The ratio $\sigma/T_c^3$ shows a scaling violation similar to that already observed for the latent heat $\latent$. However, we find that the physically interesting dimensionless combinations $(\sigma^{3}/\latent^2 T)^{1/2}$ and $\sigma T/ \latent$ scale within the statistical errors., Comment: 13 pages with 2 PostScript figures, LaTeX, CERN-TH.6798/93, AZPH-TH/93-04, UTHEP-252