521 research outputs found
First results from 2+1-Flavor Domain Wall QCD: Mass Spectrum, Topology Change and Chiral Symmetry with
We present results for the static interquark potential, light meson and
baryon masses, and light pseudoscalar meson decay constants obtained from
simulations of domain wall QCD with one dynamical flavour approximating the
quark, and two degenerate dynamical flavours with input bare masses ranging
from to approximating the and quarks. We compare these
quantities obtained using the Iwasaki and DBW2 improved gauge actions, and
actions with larger rectangle coefficients, on lattices. We seek
parameter values at which both the chiral symmetry breaking residual mass due
to the finite lattice extent in the fifth dimension and the Monte Carlo time
history for topological charge are acceptable for this set of quark masses at
lattice spacings above 0.1 fm. We find that the Iwasaki gauge action is best,
demonstrating the feasibility of using QCDOC to generate ensembles which are
good representations of the QCD path integral on lattices of up to 3 fm in
spatial extent with lattice spacings in the range 0.09-0.13 fm. Despite large
residual masses and a limited number of sea quark mass values with which to
perform chiral extrapolations, our results for light hadronic physics scale and
agree with experimental measurements within our statistical uncertainties.Comment: RBC and UKQCD Collaborations. 82 pages, 34 figures Typos correcte
FlyBase: enhancing Drosophila Gene Ontology annotations
FlyBase (http://flybase.org) is a database of Drosophila genetic and genomic information. Gene Ontology (GO) terms are used to describe three attributes of wild-type gene products: their molecular function, the biological processes in which they play a role, and their subcellular location. This article describes recent changes to the FlyBase GO annotation strategy that are improving the quality of the GO annotation data. Many of these changes stem from our participation in the GO Reference Genome Annotation Project—a multi-database collaboration producing comprehensive GO annotation sets for 12 diverse species
2+1 flavor domain wall QCD on a (2 fm)^3 lattice: light meson spectroscopy with Ls = 16
We present results for light meson masses and pseudoscalar decay constants
from the first of a series of lattice calculations with 2+1 dynamical flavors
of domain wall fermions and the Iwasaki gauge action. The work reported here
was done at a fixed lattice spacing of about 0.12 fm on a 16^3\times32 lattice,
which amounts to a spatial volume of (2 fm)^3 in physical units. The number of
sites in the fifth dimension is 16, which gives m_{res} = 0.00308(4) in these
simulations. Three values of input light sea quark masses, m_l^{sea} \approx
0.85 m_s, 0.59 m_s and 0.33 m_s were used to allow for extrapolations to the
physical light quark limit, whilst the heavier sea quark mass was fixed to
approximately the physical strange quark mass m_s. The exact rational hybrid
Monte Carlo algorithm was used to evaluate the fractional powers of the fermion
determinants in the ensemble generation. We have found that f_\pi = 127(4) MeV,
f_K = 157(5) MeV and f_K/f_\pi = 1.24(2), where the errors are statistical
only, which are in good agreement with the experimental values.Comment: RBC and UKQCD Collaborations. 17 pages, 14 figures. Typeset with
ReVTEX4. v2: replaced with the version published in PRD with improved
introductio
Observation of Parity Nonconservation in Moller Scattering
We report a measurement of the parity-violating asymmetry in fixed target
electron-electron (Moller) scattering: A_PV = -175 +/- 30 (stat.) +/- 20
(syst.) parts per billion. This first direct observation of parity
nonconservation in Moller scattering leads to a measurement of the electron's
weak charge at low energy Q^e_W = -0.053 +/- 0.011. This is consistent with the
Standard Model expectation at the current level of precision:
sin^2\theta_W(M_Z)_MSbar = 0.2293 +/- 0.0024 (stat.) +/- 0.0016 (syst.) +/-
0.0006 (theory).Comment: Version 3 is the same as version 2. These versions contain minor text
changes from referee comments and a change in the extracted value of Q^e_W
and sin^2\theta_W due to a change in the theoretical calculation of the
bremsstrahulung correction (ref. 16
Precision Measurement of the Weak Mixing Angle in Moller Scattering
We report on a precision measurement of the parity-violating asymmetry in
fixed target electron-electron (Moller) scattering: A_PV = -131 +/- 14 (stat.)
+/- 10 (syst.) parts per billion, leading to the determination of the weak
mixing angle \sin^2\theta_W^eff = 0.2397 +/- 0.0010 (stat.) +/- 0.0008 (syst.),
evaluated at Q^2 = 0.026 GeV^2. Combining this result with the measurements of
\sin^2\theta_W^eff at the Z^0 pole, the running of the weak mixing angle is
observed with over 6 sigma significance. The measurement sets constraints on
new physics effects at the TeV scale.Comment: 4 pages, 2 postscript figues, submitted to Physical Review Letter
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