Light and strange hadron spectroscopy with dynamical Wilson fermions

Light hadron spectrum with two flavors of O(a) improved dynamical quarks: final results from JLQCD

Light hadron spectrum and light quark masses from lattice QCD

We present results for the static interquark potential, lightest glueballs, light hadron spectrum, and topological susceptibility using a nonperturbatively improved action on a ${16}^{3}\ifmmode\times\else\texttimes\fi{}32$ lattice at a set of values of the bare gauge coupling and bare dynamical quark mass chosen to keep the lattice size fixed in physical units (\ensuremath{\sim}1.7 fm). By comparing these measurements with a matched quenched ensemble, we study the effects due to two degenerate flavors of dynamical quarks. With the greater control over residual lattice spacing effects which these methods afford, we find some evidence of charge screening and some minor effects on the light hadron spectrum over the range of quark masses studied ${(M}_{\mathrm{PS}}{/M}_{V}>~0.58,$ where PS denotes pseudoscalar and $V$ denotes vector). More substantial differences between quenched and unquenched simulations are observed in measurements of topological quantities.

We present results for ${f}_{B},$ ${f}_{{B}_{s}},$ ${f}_{D},$ ${f}_{{D}_{s}}$ and their ratios in the presence of two flavors of light sea quarks ${(N}_{f}=2).$ We use Wilson light valence quarks and Wilson and static heavy valence quarks; the sea quarks are simulated with staggered fermions. Additional quenched simulations with nonperturbatively improved clover fermions allow us to improve our control of the continuum extrapolation. For our central values the masses of the sea quarks are not extrapolated to the physical u, d masses; that is, the central values are ``partially quenched.'' A calculation using ``fat-link clover'' valence fermions is also discussed but is not included in our final results. We find, for example, ${f}_{B}{=190(7)(}_{\ensuremath{-}17}^{+24}{)(}_{\ensuremath{-}2}^{+11}{)(}_{\ensuremath{-}0}^{+8})\mathrm{MeV},$ ${f}_{{B}_{s}}{/f}_{B}{=1.16(1)(2)(2)(}_{\ensuremath{-}0}^{+4}),$ ${f}_{{D}_{s}}{=241(5)(}_{\ensuremath{-}26}^{+27}{)(}_{\ensuremath{-}4}^{+9}{)(}_{\ensuremath{-}0}^{+5})\mathrm{MeV},$ and ${f}_{B}{/f}_{{D}_{s}}{=0.79(2)(}_{\ensuremath{-}4}^{+5}{)(3)(}_{\ensuremath{-}0}^{+5}),$ where in each case the first error is statistical and the remaining three are systematic: the error within the partially quenched ${N}_{f}=2$ approximation, the error due to the missing strange sea quark and to partial quenching, and an estimate of the effects of chiral logarithms at small quark mass. The last error, though quite significant in decay constant ratios, appears to be smaller than has been recently suggested by Kronfeld and Ryan, and Yamada. We emphasize, however, that as in other lattice computations to date, the lattice $u,d$ quark masses are not very light and chiral log effects may not be fully under control.

Deriving the light hadron spectrum from first principles of QCD has been a fundamental issue in elementary particle physics since the mid-1970s, when QCD was established. With this goal in mind, we have carried out large-scale simulations of lattice QCD on the CPPACS computer. In this article, we present results for the light hadron spectrum derived in the quenched approximation to lattice QCD. We find that although the global structure of the observed spectrum is reproduced, the quenched spectrum systematically deviates from experiment when examined with an accuracy at better than a 10% level. Results for light quark masses are also reported. Another simulation of full QCD done recently (also on the CP-PACS computer) shows indications that the discrepancy observed in quenched QCD is significantly reduced by the introduction of two flavors of light dynamical quarks.

We study the sigma term and the strange quark content of nucleon in 2+1-flavor QCD with dynamical overlap fermions. We analyze the lattice data of nucleon mass taken at two different strange quark masses with five values of up and down quark mass es each. Using the reweighting technique, we study the strange quark mass dependence of the nucleon and extract the strange quark content.

We investigate the mass differences of charm and bottom heavy baryons, using MILC lattice gauge configurations with 2+1 dynamical sea quark flavors. We extend our previous work to three lattice spacings: fine (a~0.09), coarse (a~0.12), and medium-coarse (a~0.15) ensembles. For extrapolations and interpolations, we apply simultaneous quadratic fits and simple linear fits with the full QCD data points for the valence quark masses as well as the sea quark masses.

Light hadron spectrum with Kogut-Susskind quarks

The effect of sea quark electromagnetic charge on meson masses is investigated, and first results for full QED+QCD low-energy constants are presented. The electromagnetic charge for sea quarks is incorporated in quenched QED+full QCD lattice simulations by a reweighting method. The reweighting factor, which connects quenched and unquenched QED, is estimated using a stochastic method on 2+1 flavor dynamical domain-wall quark ensembles.

Light hardon properties with improved staggered quarks

Light hadron spectrum — MILC results with the Kogut-Susskind and Wilson actions

Abundant strange sea quarks in the nucleon and flavor asymmetry of the light sea quarks in the octet baryon at small x

We present the first next-to-leading-order QCD analysis of neutrino charm production, using a sample of 6090ν μ − and $$\bar \nu _\mu $$ -induced opposite-sign dimuon events observed in the CCFR detector at the Fermilab Tevatron. We find that the nucleon strange quark content is suppressed with respect to the non-strange sea quarks by a factor κ=0.477 −0.053 +0.063 , where the error includes statistical, systematic and QCD scale uncertainties. In contrast to previous leading order analyses, we find that the strange seax-dependence is similar to that of the non-strange sea, and that the measured charm quark mass,m c =1.70±0.19 GeV/c2, is larger and consistent with that determined in other processes. Further analysis finds that the difference inx-distributions betweenxs(x) and $$x\bar s{\text{(}}x{\text{)}}$$ is small. A measurement of the Cabibbo-Kobayashi-Maskawa matrix element |V cd |=0.232 −0.020 +0.018 is also presented.

The reduced matrix elements a_2 and d_2 are computed in lattice QCD with N_f=2 flavors of light dynamical (sea) quarks. For proton and neutron targets we obtain as our best estimates d_2^(p)=0.004(5) and d_2^(n)=-0.001(3), respectively, in the MSbar scheme at Q^2=5 GeV^2, while for a_2 we find a_2^(p)=0.077(12) and a_2^(n)=-0.005(5), where the errors are purely statistical.

Objective To compare the accuracies of water arsenic testing of AFS-230E-type atomic fluorescence photometer by linear and quadratic curve fitting. Methods AFS-230E-type atomic fluorescence photometer was used to detect the fluorescence intensity of the standard samples. Two series of data, the fluorescence intensity and the standard concentration were fitted with a straight line and a curve. Their fitting concentration was calculated with their samples' fitting equation and fluorescence intensity respectively. Results When the water arsenic concentration was in the range of 0.1-5.0 μg/L, the total error value was 7.79% in linear fitting, 3.67 % in curve fitting, and the calculations were of no significant differences with the linear and curve fitting(t=1.664, P > 0.05). When the water arsenic concentration was in the range of 1-20 μg/L,the total error value was 9.26% percent in linear fitting, 2.44% in curve fitting, and the calculation results were of significant difference with the linear and curve fitting(t=2.63, P < 0.05). Conclusions When the water arsenic concentration in the range of 0.1-5.0 μg/L, the linear fitting which is default in the instrument can be used directly. When the water arsenic concentration in the range of 1.0-20.0 μg/L, the curve fitting should be used because its test results are more accurately compared with the linear fitting. Key words: Fluorophotometry; Arsenic; Outcome assessment