Pentaquark baryons with Charm

This paper has been withdrawn.Comment: This paper has been withdraw

Perturbation calculation of the axial anomaly of Ginsparg-Wilson fermion

We evaluate the axial anomaly for the general Ginsparg-Wilson fermion operator D = D_c (\Id + R D_c)^{-1} with R = r \Id. For any chirally symmetric $D_c$ which in the free fermion limit, is free of species doubling and behaves like $i \gamma_\mu p_\mu$ as $p \to 0$, the axial anomaly \tr[\gamma_5 (R D) (x,x)] for U(1) lattice gauge theory with single fermion flavor is equal to $e^2/(32 \pi^2) \epsilon_{\mu\nu\lambda\sigma} F_{\mu\nu}(x) F_{\lambda\sigma}(x+\hat\mu+\hat\nu)$ plus terms which are higher orders and/or non-perturbative contribtuons. The $F \tilde{F}$ term is r-invariant and has the correct continuum limit.Comment: 38 pages, latex, 1 figure, add appendix C and several remark

Light quark masses, chiral condensate and quark-gluon condensate in quenched lattice QCD with exact chiral symmetry

We determine several quantities in quenched lattice QCD with exact chiral symmetry. For 100 gauge configurations generated with Wilson gauge action at $\beta = 6.0$ on the $16^3 \times 32$ lattice, we compute quenched quark propagators for 13 bare quark masses. The pion decay constant is extracted from the pion propagator, and from which the inverse lattice spacing is determined to be $a^{-1} = 1.979(6)$ GeV. The parameters ($C, \delta, B$) in the pseudoscalar meson mass formula in quenched chiral perturbation theory (q$\chi$PT) to one-loop order are determined. Further, we measure the index (topological) susceptibility of these 100 gauge configurations, $\chi_t = (175 \pm 6 {MeV})^4$, from which we obtain an estimate of the mass of $\eta'$ in q$\chi$PT, and the coefficient of quenched chiral logarithm, both in good agreement with the values determined from the pion masses, as well as with the theoretical estimates. With our values of $C, \delta, B$, the experimental inputs of pion and kaon masses, and the pion decay constant, we determine the light quark masses: $m_{u,d} = 4.1 \pm 0.3$ MeV, and $m_s = 92 \pm 9$ MeV, in the $\bar{MS}$ scheme at scale $\mu = 2$ GeV. Also, we determine the quark condensate $= -(250 \pm 3 {MeV})^3$, and the quark-gluon condensate $g = -(434 \pm 4 {MeV})^5$, in the $\bar{MS}$ scheme at scale 2 GeV.Comment: 24 pages, 9 figures, the version to appear in Nucl.Phys.

Signal of Theta^+ in quenched lattice QCD with exact chiral symmetry

We investigate the mass spectrum of the pentaquark baryon ($udud \bar s$) in quenched lattice QCD with exact chiral symmetry. Using 3 different interpolating operators, we measure their $3 \times 3$ correlation matrix and obtain the eigenvalues $A^{\pm} (t)$ with $\pm$ parity, for 100 gauge configurations generated with Wilson gauge action at $\beta = 6.1$ on the $20^3 \times 40$ lattice. For the lowest-lying $J^P = 1/2^-$ state, its effective mass is almost identical to that of the KN s-wave, while for the lowest-lying $J^P = 1/2^+$ state, its effective mass is smaller than that of the KN p-wave, especially for the regime $m_u < m_s$. By chiral extrapolation (linear in $m_\pi^2$) to $m_\pi = 135$ MeV, we obatin the masses of the lowest-lying states: $m(1/2^-) = 1424(57)$ MeV and $m(1/2^+) = 1562(121)$ MeV, in agreement with the masses of $m_K + m_N \simeq 1430$ MeV and $\Theta^+(1540)$ respectively.Comment: 8 pages, 3 figures, to appear in the Proceedings of PENTAQUARK 2004, SPring8, Japan, July 20-23, 200

N(N*) and Delta(Delta*) on the lattice

We investigate the mass spectrum of Nucleon and Delta (and its counterparts with strange and charm), and their excited states, in quenched lattice QCD with exact chiral symmetry. For each light baryon, we use 23 masses to determine the coefficients of the mass formula in quenched chiral perturbation theory. By chiral extrapolation to m_\pi=135 MeV, we obtain M_N=958(26) MeV, M_{N*}=1553(42) MeV, M_{Delta}=1216(32) MeV and M_{Delta*}=1611(17) MeV, which are identified with N(939)P_{11},N(1535)S_{11}, Delta(1232)P_{33} and Delta(1620)S_{31} respectively. Further, we directly measure the masses of Omega^{-}, M_{Omega}=1648(60) MeV, and its excited state, M_{Omega*}=1935(48) MeV; as well as the triply charmed baryon Omega_{ccc}^{++}, M_{Omega_{ccc}^{++}}=4931(22) MeV, and its excited state, M_{{\Omega^{++}_{ccc}}^*}=5185(35) MeV.Comment: 11 pages, 4 figure

Projection of the low-lying eigenmodes of the overlap Dirac operator in lattice QCD

We outline our implementation of the adaptive thick-restart Lanczos algorithm ($a$-TRLan) for the projection of the low-lying eigenmodes of the overlap Dirac operator in lattice QCD, and compare the performances of our code and the widely used package ARPACK.Comment: 9 pages, 2 figures, presented at the 2013 International Workshop on Computational Science and Enginnering, 14-17 October 2013, Taipei, Taiwa

Bs and Bc mesons in lattice QCD with exact chiral symmetry

We determine the masses and decay constants of the pseudoscalar mesons Bs and Bc, and also the masses of the vector mesons Bs^* and Bc^*, in quenched lattice QCD with exact chiral symmetry. For 100 gauge configurations generated with single-plaquette action at beta = 7.2 on the 32^3 x 60 lattice, we compute point-to-point quark propagators for 33 quark masses in the range [0.01, 0.85], and measure the time-correlation functions of pseudoscalar and vector mesons. The inverse lattice spacing and the charm quark bare mass are determined using the mass and decay constant of eta_c(2980). The bare masses of s and b quarks are chosen such that the masses of the corresponding vector mesons are in good agreement with phi(1020), and Upsilon(9460) respectively. Our results are: m_{Bs} = 5385(27)(17) MeV, f_{Bs} = 253(8)(7) MeV, m_{Bc} = 6278(6)(4) MeV, f_{Bc} = 489(4)(3) MeV, m_{Bs^*} = 5424(28)(19) MeV, and m_{Bc^*} = 6315(6)(5) MeV.Comment: 7 pages, an update of the published version in the Proceedings of Lattice 2006, Tucson, Arizona, July 23-28, 200

One-flavor algorithm for Wilson and domain-wall fermions

We construct positive-definite pseudofermion actions for one fermion flavor in lattice field theory, for Wilson and domain-wall fermions respectively. The positive definiteness of these actions ensures that they can be simulated with the Hybrid Monte Carlo (HMC) method. For lattice QCD with optimal domain-wall quarks, we compare the efficiency of HMC simulations of 2-flavor and (1+1)-flavor, and find that the efficiency ratio is about 3:2.Comment: 7 pages. Talk presented at the XXVII International Symposium on Lattice Field Theory, July 26-31 2009, Peking University, Beijing, Chin

The spectrum of charmonium-like vector mesons in lattice QCD

We present the first lattice results of the spectrum of exotic vector mesons extracted from the molecular and diquark-antidiquark operators, with quark fields c-q-cbar-qbar, and c-s-cbar-qbar (c-q-cbar-sbar) respectively, in lattice QCD with exact chiral symmetry. Our results suggest that X(3872) and Y(4260) are in the spectrum of QCD, with J^{PC} = 1^{++} and 1^{--} respectively. Moreover, we obtain the spectrum of heavier exotic mesons with c-s-cbar-ubar (c-u-cbar-sbar), c-s-cbar-dbar (c-d-cbar-sbar), c-s-cbar-sbar, and c-c-cbar-cbar, as the first theoretical predictions from lattice QCD.Comment: 7 pages, based on talks given at Lattice 2006, Tucson, Arizona, July 23-28, 2006, and at The International Workshop on B Factories and New Measurements (BNM2006) at KEK, Japan, September 13-14, 200

Y(4260) on the lattice

We investigate the mass spectra of closed-charm mesons with $J^{PC} = 1^{--}$, for hybrid charmonium, molecules, and diquark-antidiquark operators, in quenched lattice QCD with exact chiral symmetry. For two lattice volumes $24^3 \times 48$ and $20^3 \times 40$, each of 100 gauge configurations generated with single-plaquette action at $\beta = 6.1$, we compute point-to-point quark propagators and measure the time-correlation functions of these exotic meson operators. For the molecular operator \{(\qbar\gamma_5\gamma_i\c)(\cbar\gamma_5\q)- (\cbar\gamma_5\gamma_i\q)(\qbar\gamma_5\c) \} , it detects a resonance with mass around $4238 \pm 31$ MeV, which is naturally identified with $Y(4260)$. Further, for any molecular and diquark-antidiquark operator, it detects heavier exotic charmed mesons, with quark content (\c\s\cbar\sbar) around $4450 \pm 100$ MeV, and (\c\c\cbar\cbar) around $6400 \pm 50$ MeV.Comment: 17 pages, 13 EPS figures, v3:reference added, accepted for publication in Physical Review