325 research outputs found
Development of Flutter Constraints for High-fidelity Aerostructural Optimization
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143080/1/6.2017-4455.pd
The Hyperfine Splitting in Charmonium: Lattice Computations Using the Wilson and Clover Fermion Actions
We compute the hyperfine splitting on the lattice,
using both the Wilson and -improved (clover) actions for quenched quarks.
The computations are performed on a lattice at ,
using the same set of 18 gluon configurations for both fermion actions. We find
that the splitting is 1.83\err{13}{15} times larger with the clover action than
with the Wilson action, demonstrating the sensitivity of the spin-splitting to
the magnetic moment term which is present in the clover action. However, even
with the clover action the result is less than half of the physical
mass-splitting. We also compute the decay constants and
, both of which are considerably larger when computed using
the clover action than with the Wilson action. For example for the ratio
we find 0.32\err{1}{2} with the Wilson action
and with the clover action (the physical value is 0.44(2)).Comment: LaTeX file, 8 pages and two postscript figures. Southampton Preprint:
SHEP 91/92-27 Edinburgh Preprint: 92/51
Gauge Invariant Smearing and Matrix Correlators using Wilson Fermions at beta=6.2
We present an investigation of gauge invariant smearing for Wilson fermions
on a lattice at . We demonstrate a smearing
algorithm that allows a substantial improvement in the determination of the
baryon spectrum obtained using propagators smeared at both source and sink, at
only a small computational cost. We investigate the matrix of correlators
constructed from local and smeared operators, and are able to expose excited
states of both the mesons and baryons.Comment: at lattice `92. 4 pages latex + 3 postscript figures. Edinburgh
preprint: 92/51
Current Renormalisation Constants with an O(a)-improved Fermion Action
Using chiral Ward identities, we determine the renormalisation constants of
bilinear quark operators for the Sheikholeslami-Wohlert action lattice at
beta=6.2. The results are obtained with a high degree of accuracy. For the
vector current renormalisation constant we obtain Z_V=0.817(2)(8), where the
first error is statistical and the second is due to mass dependence of Z_V.
This is close to the perturbative value of 0.83. For the axial current
renormalisation constant we obtain Z_A = 1.045(+10 -14), significantly higher
than the value obtained in perturbation theory. This is shown to reduce the
difference between lattice estimates and the experimental values for the
pseudoscalar meson decay constants, but a significant discrepancy remains. The
ratio of pseudoscalar to scalar renormalisation constants, Z_P/Z_S, is less
well determined, but seems to be slightly lower than the perturbative value.Comment: 8 pages uuencoded compressed postscript file. Article to be submitted
to Phys.Rev.
Continuum Limit of from 2+1 Flavor Domain Wall QCD
We determine the neutral kaon mixing matrix element in the continuum
limit with 2+1 flavors of domain wall fermions, using the Iwasaki gauge action
at two different lattice spacings. These lattice fermions have near exact
chiral symmetry and therefore avoid artificial lattice operator mixing.
We introduce a significant improvement to the conventional NPR method in
which the bare matrix elements are renormalized non-perturbatively in the
RI-MOM scheme and are then converted into the MSbar scheme using continuum
perturbation theory. In addition to RI-MOM, we introduce and implement four
non-exceptional intermediate momentum schemes that suppress infrared
non-perturbative uncertainties in the renormalization procedure. We compute the
conversion factors relating the matrix elements in this family of RI-SMOM
schemes and MSbar at one-loop order. Comparison of the results obtained using
these different intermediate schemes allows for a more reliable estimate of the
unknown higher-order contributions and hence for a correspondingly more robust
estimate of the systematic error. We also apply a recently proposed approach in
which twisted boundary conditions are used to control the Symanzik expansion
for off-shell vertex functions leading to a better control of the
renormalization in the continuum limit.
We control chiral extrapolation errors by considering both the NLO SU(2)
chiral effective theory, and an analytic mass expansion. We obtain
B_K^{\msbar}(3 GeV) = 0.529(5)_{stat}(15)_\chi(2)_{FV}(11)_{NPR}. This
corresponds to . Adding
all sources of error in quadrature we obtain , with an overall combined error of 3.6%.Comment: 65 page
- …