Ds mesons are studied in three quantum channels (J P =

A numerical simulation of quenched QCD on a 24 X 12 X 12 X 24 lattice at /3= 5.9 is used to calculate the electric and magnetic form factors of the baryon octet. General forms of the baryon interpolating fields are considered. Magnetic moments, electric radii, magnetic radii, and magnetic transition moments are extracted from the form factors. The electric properties are found to be consistent with a quark-model picture involving spin-dependent forces. The lattice results for the magnetic properties show a mass and spin dependence of the effective quark moments which is not accounted for in conventional quark models. Lattice calculations underestimate the magnitude of electric radii, magnetic radii, and magnetic moments compared to experimental measurements. The finite volume of the periodic lattice may be responsible for the discrepancies. The pattern of electromagnetic radii in the lattice results are seen to be generally reproduced in the model results that are considered. The only exception is that of Z-which proves to be a sensitive probe of the quark dynamics. Lattice calculations indicate a positive value for the normalized square magnetic radius in Z-which contrasts Skyrme model results. Ratios of the magnetic moments allow a more detailed comparison with the experimental measurements. The lattice calculations are seen to better reproduce the experimental ratios than the model calculations.

The electromagnetic properties of the SU (3)-flavor baryon decuplet are examined within a lattice simulation of quenched QCD. Electric charge radii, magnetic moments, and magnetic radii are extracted from the E0 and M 1 form factors. Preliminary results for the E2 and M 3 moments are presented giving the first model independent insight to the shape of the quark distribution in the baryon ground state. As in our octet baryon analysis, the lattice results give evidence of spin-dependent forces and mass effects in the electromagnetic properties. The quark charge distribution radii indicate these effects act in opposing directions. Some baryon dependence of the effective quark magnetic moments is seen. However, this dependence in decuplet baryons is more subtle than that for octet baryons. Of particular interest are the lattice predictions for the magnetic moments of Ω − and ∆ ++ for which new recent experimental measurements are available. The lattice prediction of the ∆ ++ /p ratio appears larger than the experimental ratio, while the lattice prediction for the Ω − /p magnetic moment ratio is in good agreement with the experimental ratio.

A first exploratory lattice QCD simulation is presented aimed at extracting the masses and widths of the broad scalar D * 0 (2400) and the axial D1(2430) charm-light resonances. For that purpose Dπ and D * π scattering are simulated, and the resonance parameters are extracted using a Breit-Wigner fit of the resulting phase shifts. We use a single two-flavor dynamical ensemble with mπ ≈ 266 MeV, a ≃ 0.124 fm and a rather small volume V = 16 3 × 32. The resulting D * 0 (2400) mass is 351 ± 21 MeV above the spin-average 1 4(mD + 3mD * ), in agreement with the experimental value of 347 ± 29 MeV above. The resulting D * 0 → Dπ coupling g lat = 2.55 ± 0.21 GeV is close to the experimental value g exp ≤ 1.92 ± 0.14 GeV, where g parametrizes the width Γ ≡ g 2 p * /s. The resonance parameters for the broad D1(2430) are also found close to the experimental values; these are obtained by appealing to the heavy quark limit, where the neighboring resonance D1(2420) is narrow. The calculated I = 1/2 scattering lengths are a0 = 0.81 ± 0.14 fm for Dπ and a0 = 0.81 ± 0.17 fm for D * π scattering. The simulation of the scattering in these channels incorporates quark-antiquark as well as multi-hadron interpolators, and the distillation method is used for contractions. In addition, the ground and several excited charm-light and charmonium states with various J P are calculated using standard quark-antiquark interpolators.

The mass spectrum of charmed and bottom baryons is computed on anisotropic lattices using quenched lattice nonrelativistic QCD. The masses are extracted by using mass splittings which are more accurate than masses obtained directly by using the nonrelativistic mass-energy relation. Of particular interest are the mass splittings between spin-1/2 and spin-3/2 heavy baryons, and we find that these color hyperfine effects are not suppressed in the baryon sector although they are known to be suppressed in the meson sector. The results are compared with those obtained in a previous nonrelativistic QCD calculation and with those obtained from a Dirac-Wilson action of the D234 type.

No abstract

The scalar meson D*(s0)(2317) is found 37(17) MeV below the DK threshold in a lattice simulation of the J(P)=0(+) channel using, for the first time, both DK as well as s¯c interpolating fields. The simulation is done on N(f)=2+1 gauge configurations with m(π) is approximately equal to 156 MeV, and the resulting M(D*(s0))-1/4(M(D(s))+3M(D*(s)))=266(16) MeV is close to the experimental value 241.5(0.8) MeV. The energy level related to the scalar meson is accompanied by additional discrete levels due to DK scattering states. The levels near threshold lead to the negative DK scattering length a(0)=-1.33(20) fm that indicates the presence of a state below threshold.

We use lattice QCD simulations, with MILC gluon configurations and HISQ c-quark propagators, to make very precise determinations of moments of charm-quark pseudoscalar, vector and axialvector correlators. These moments are combined with new four-loop results from continuum perturbation theory to obtain several new determinations of the MS mass of the charm quark and of the MS coupling. We find mc(3 GeV) = 0.986 (10) GeV, or, equivalently, mc(mc) = 1.268 (9) GeV, both for n f = 4 flavors; and α MS (3 GeV, n f = 4) = 0.251 (6), or, equivalently, α MS (MZ , n f = 5) = 0.1174 (12). The new mass agrees well with results from continuum analyses of the vector correlator using experimental data for e + e − annihilation (instead of using lattice QCD simulations). These lattice and continuum results are the most accurate determinations to date of this mass. Ours is also one of the most accurate determinations of the QCD coupling by any method.