First results from the asymmetric O(a) improved Fermilab action

We present first results from calculations using O(a) improved (FNAL) space-time asymmetric action on a 12^3 x 24 quenched lattice at \beta = 5.7 and c_SW = 1.57. The asymmetry parameter is determined non-perturbatively from the energy-momentum dispersion relation. This improvement scheme is mass dependent, and the calculations have been done in the charm and bottom quark mass sectors since it is at these heavier masses that the asymmetry is expected to be relevant.Comment: 3 pp. LaTeX2e, 6PostScript figures, uses espcrc2.sty. Contribution to Lattice99 (Pisa) proceedings (Improvement and Renormalisation

Properties of Low-Lying Heavy-Light Mesons

We present preliminary results for the B meson decay constant and masses of low-lying heavy-light mesons in the static limit. Calculations were performed on the lattice in the quenched approximation using multistate smearing functions generated from a Hamiltonian for a spinless relativistic quark. The 2S--1S and 1P--1S mass splittings are measured. Using the 1P--1S charmonium splitting to set the overall scale, the ground state decay constant, f_B, is 319 +- 11 (stat) MeV.Comment: 8 pages, 9 figures, UCLA/92/TEP/4

Unquenched QCD with Light Quarks

We present recent results in unquenched lattice QCD with two degenerate light sea quarks using the truncated determinant approximation (TDA). In the TDA the infrared modes contributing to the quark determinant are computed exactly up to some cutoff in quark off-shellness (typically 2$\Lambda_{QCD}$). This approach allows simulations to be performed at much lighter quark masses than possible with conventional hybrid MonteCarlo techniques. Results for the static energy and topological charge distributions are presented using a large ensemble generated on very coarse (6$^4$) but physically large lattices. Preliminary results are also reported for the static energy and meson spectrum on 10$^3$x20 lattices (lattice scale $a^{-1}$=1.15 GeV) at quark masses corresponding to pions of mass $\leq$ 200 MeV. Using multiboson simulation to compute the ultraviolet part of the quark determinant the TDA approach becomes an exact with essentially no increase in computational effort. Some preliminary results using this fully unquenched algorithm are presented.Comment: LateX, 39 pages, 16 eps figures, 1 ps figur

Light Quark Masses with an O(a)-Improved Action

We present the recent Fermilab calculations of the masses of the light quarks, using tadpole-improved Sheikholeslami-Wohlert (SW) quarks. Various sources of systematic errors are studied. Our final result for the average light quark mass in the quenched approximation evaluated in the $\bar{MS}$ scheme is $\bar{m}_q(\mu=2 GeV;n_f=0)= (m_u+m_d)/2=3.6 \pm 0.6 MeV$.Comment: 3 pgs. 3 figures. espcrc2.sty included. Talk presented at LATTICE96(phenomenology

Anomalous Chiral Behavior in Quenched Lattice QCD

A study of the chiral behavior of pseudoscalar masses and decay constants is carried out in quenched lattice QCD with Wilson fermions. Using the modified quenched approximation (MQA) to cure the exceptional configuration problem, accurate results are obtained for pion masses as low as $\approx$ 200 MeV. The anomalous chiral log effect associated with quenched $\eta'$ loops is studied in both the relation between $m_{\pi}^2$ vs. $m_q$ and in the light-mass behavior of the pseudoscalar and axial vector matrix elements. The size of these effects agrees quantitatively with a direct measurement of the $\eta'$ hairpin graph, as well as with a measurement of the topological susceptibility, thus providing several independent and quantitatively consistent determinations of the quenched chiral log parameter $\delta$. For $\beta=5.7$ with clover-improved fermions $(C_{sw} =1.57)$ all results are consistent with $\delta=0.065\pm 0.013$ .Comment: 51 pages, 20 figures, Late

Phonemic – Morphemic dissociation in university students with dyslexia:An index of reading compensation?

A phonological deficit constitutes a primary cause of developmental dyslexia, which persists into adulthood and can explain some aspects of their reading impairment. Nevertheless, some dyslexic adults successfully manage to study at university level, although very little is currently known about how they achieve this. The present study investigated at both the individual and group level, whether the development of another oral language skill, namely, morphological knowledge can be preserved and dissociated from the development of phonological knowledge. Reading, phonological and morphological abilities were measured in 20 dyslexic and 20 nondyslexic university students. The results confirmed the persistence of deficits in phonological but not morphological abilities, thereby revealing a dissociation in the development of these two skills. Moreover, the magnitude of the dissociation correlated with reading level. The outcome supports the claim that university students with dyslexia may compensate for phonological weaknesses by drawing on morphological knowledge in reading

Stellar Nucleosynthesis in the Hyades Open Cluster

We report a comprehensive light element (Li, C, N, O, Na, Mg, and Al) abundance analysis of three solar-type main sequence (MS) dwarfs and three red giant branch (RGB) clump stars in the Hyades open cluster using high-resolution and high signal-to-noise spectroscopy. For each group (MS or RGB), the CNO abundances are found to be in excellent star-to-star agreement. Our results confirm that the giants have undergone the first dredge-up and that material processed by the CN cycle has been mixed to the surface layers. The observed abundances are compared to predictions of a standard stellar model based on the Clemson-American University of Beirut (CAUB) stellar evolution code. The model reproduces the observed evolution of the N and O abundances, as well as the previously derived 12C/13C ratio, but it fails to predict by a factor of 1.5 the observed level of 12C depletion. Li abundances are derived to determine if non-canonical extra mixing has occurred in the Hyades giants. The Li abundance of the giant gamma Tau is in good accord with the predicted level of surface Li dilution, but a ~0.35 dex spread in the giant Li abundances is found and cannot be explained by the stellar model. Possible sources of the spread are discussed; however, it is apparent that the differential mechanism responsible for the Li dispersion must be unrelated to the uniformly low 12C abundances of the giants. Na, Mg, and Al abundances are derived as an additional test of our stellar model. All three elements are found to be overabundant by 0.2-0.5 dex in the giants relative to the dwarfs. Such large enhancements of these elements are not predicted by the stellar model, and non-LTE effects significantly larger (and, in some cases, of opposite sign) than those implied by extant literature calculations are the most likely cause.Comment: 40 pages, 6 figures, 6 tables; accepted by Ap

The continuum limit of fBf_B from the lattice in the static approximation

We present an analysis of the continuum extrapolation of $f_B$ in the static approximation from lattice data. The method described here aims to uncover the systematic effects which enter in this extrapolation and has not been described before. Our conclusions are that we see statistical evidence for scaling of $f_B^{stat}$ for inverse lattice spacings \gtap 2 GeV but not for \ltap 2 GeV. We observe a lack of {\em asymptotic} scaling for a variety of quantities, including $f_B^{stat}$, at all energy scales considered. This can be associated with finite lattice spacing systematics. Once these effects are taken into account, we obtain a value of 230(35) MeV for $f_B^{stat}$ in the continuum where the error represents uncertainties due to both the statistics and the continuum extrapolation. In this method there is no error due to uncertainties in the renormalization constant connecting the lattice and continuum effective theories.Comment: 33 pages, latex text file and postscript figures all uuencoded into a single file, ROME preprint 94/104

Properties of B-Mesons in Lattice QCD

The results of an extensive study of B-meson properties in quenched lattice QCD are presented. The studies are carried out in the static quark limit where the b-quark is taken to be infinitely massive. Our computations rely on a multistate smearing method introduced previously, with smearing functions generated from a relativistic lattice quark model. Systematic errors arising from excited state contamination, finite volume effects, and the chiral extrapolation for the light quarks are estimated. We obtain continuum results for the mass splitting M_{B_s}- M_{B_u} = 86 (+/-)12(stat) {+7/-9}(syst) MeV, the ratio of decay constants f_{B_s}/f_{B_u} = 1.22 (+/-)0.04(stat) (+/-)0.02 (syst). For the B-meson decay constant we separately exhibit the sizable uncertainties in the extrapolation to the continuum limit a -> 0 and higher order perturbative matching. We obtain f_{B} = 188 (+/-)23(stat) (+/-)15(syst) {+26/-0}(extrap) (+/-)14 (pert) MeV. ----- [Postscript version of paper available by anonymous ftp at fncrd6.fnal.gov. The file is fb.ps in subdirectory theory.]Comment: 75 pages, FERMILAB-PUB-94/164-