607 research outputs found
The Laplacian Gauge Gluon Propagator in SU(N_c)
We examine the gluon propagator in the Laplacian gauge in quenched lattice
QCD as a function of the number of colours. We observe a weak dependence on
over the whole momentum range. This implies an almost -independent
gluon pole mass in units of the string tension.Comment: 5 pages, 7 figures. A study of the gluon propagator in SU(4) for
various lattice sizes was added. Extended version to appear in Phys. Rev.
Nucleon to Delta transition form factors with domain wall fermions
We calculate the electromagnetic, axial and pseudo-scalar form factors of the
Nucleon to transition using two dynamical light degenerate
quarks and a dynamical strange quark simulated with the domain wall fermion
action. Results are obtained at lattice spacings fm and
fm, with corresponding pion masses of MeV and MeV, respectively.
High statistics measurements are achieved by utilizing the coherent sink
technique. The dominant electromagnetic dipole form factor, the axial form
factors and the pseudo-scalar coupling are extracted to a good accuracy. This
allows the investigation of the non-diagonal Goldberger-Treiman relation.
Particular emphasis is given on the extraction of the sub-dominant
electromagnetic quadrupole form factors and their ratio to the dominant dipole
form factor, and , measured in experiment.Comment: 31 pages, 10 figure
Matching the High Momentum Modes in a Truncated Determinant Algorithm
Within a truncated determinant algorithm, two alternatives are discussed for
including systematically the remaining ultraviolet modes. Evidence is presented
that these modes are accurately described by an effective action involving only
small Wilson loops.Comment: LATTICE98(algorithms) ; typos correcte
The Infrared behaviour of the gluon propagator in SU(2) and SU(3) without lattice Gribov copies
We present lattice results for the gluon propagator for SU(2) and SU(3) in the Laplacian gauge which avoids lattice Gribov copies. In SU(3) we compare with the most recent lattice calculation in Landau gauge and with various approximate solutions of the Dyson Schwinger equations (DSE)
Gluon propagator without lattice Gribov copies
We study the gluon propagator in quenched lattice QCD using the Laplacian gauge which is free of lattice Gribov copies. We compare our results with those obtained in the Landau gauge on the lattice, as well as with various approximate solutions of the Dyson-Schwinger equations. We find a finite value ~(445 MeV)–2 for the renormalized zero-momentum propagator (taking our renormalization point at 1.943 GeV) and a pole mass ~640±140 MeV
Determination of the axial and pseudoscalar form factors from lattice QCD
We present a lattice QCD calculation of the matrix elements of
the axial-vector and pseudoscalar currents. The decomposition of these matrix
elements into the appropriate Lorentz invariant form factors is carried out and
the techniques to calculate the form factors are developed and tested using
quenched configurations. Results are obtained for 2+1 domain wall fermions and
within a hybrid scheme with domain wall valence and staggered sea quarks. Two
Goldberger-Treiman type relations connecting the axial to the pseudoscalar
effective couplings are derived. These and further relations based on the
pion-pole dominance hypothesis are examined using the lattice QCD results,
finding support for their validity. Utilizing lattice QCD results on the axial
charges of the nucleon and the , as well as the nucleon-to-
transition coupling constant, we perform a combined chiral fit to all three
quantities and study their pion mass dependence as the chiral limit is
approached
N-Delta(1232) axial form factors from weak pion production
The N-Delta axial form factors are determined from neutrino induced pion
production ANL & BNL data by using a state of the art theoretical model, which
accounts both for background mechanisms and deuteron effects. We find
violations of the off diagonal Goldberger-Treiman relation at the level of 2
sigma which might have an impact in background calculations for T2K and
MiniBooNE low energy neutrino oscillation precision experiments.Comment: 4 pages, 1 figur
The Leptonic Decay Constants of Mesons and the Lattice Resolution
We present a high statistics study of the leptonic decay constant of
heavy pseudoscalar mesons using propagating heavy Wilson quarks within the
quenched approximation, on lattices covering sizes from about 0.7~fm to 2~fm.
Varying between 5.74 and 6.26 we observe a sizeable dependence of
when one uses the quark field normalization that was suggested by
Kronfeld and Mackenzie, compared with the weaker dependence observed for the
standard relativistic norm. The two schemes come into agreement when one
extrapolates to . The extrapolations needed to reach the
continuum quantity introduce large errors and lead to the value
~GeV in the quenched approximation. This suggests that much more
effort will be needed to obtain an accurate lattice prediction for .Comment: 11 pages Latex + 5 tables + 8 postscript figures, unix shell archive,
DESY preprint DESY 93-17
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