31 research outputs found
Quenched Staggered Spectrum at Beta=6.0, 6.2 and 6.4
We give a preliminary report on the hadron spectrum on an ensemble of
quenched lattices at values of 6.0, 6.2 and 6.4, using staggered
fermions and collaborators Rajan Gupta and Steve Sharpe. Because of the
relatively small number of configurations we pay marginally more attention to
the question of statistics than in previous analyses. We are unable to
discredit quenched QCD.Comment: 4 pages of PostScrip
Testing improved staggered fermions with and
We study the improvement of staggered fermions using hypercubically smeared
(HYP) links. We calculate the strange quark mass and the kaon B-parameter,
, in quenched QCD on a lattice at . We find
MeV and , where the first error is from
statistics and fitting, and the second from using one-loop matching factors.
The scale (GeV) is set by , and is determined using the
kaon mass. Comparing to quenched results obtained using unimproved staggered
fermions and other discretizations, we argue that the size of discretization
errors in is substantially reduced by improvement.Comment: 9 pages, 12 figure, referee's comments are incorporate
Is strong CP invariance due to a massless up quark?
A standing mystery in the Standard Model is the unnatural smallness of the
strong CP violating phase. A massless up quark has long been proposed as one
potential solution. A lattice calculation of the constants of the chiral
Lagrangian essential for the determination of the up quark mass, 2 alpha_8 -
alpha_5, is presented. We find 2 alpha_8 - alpha_5 = 0.29 +/- 0.18, which
corresponds to m_u / m_d = 0.410 +/- 0.036. This is the first such calculation
using a physical number of dynamical light quarks, N_f = 3.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Lett., corrected small
normalization error in f_pi (conclusions were unaffected), improved lattice
spacing analysis, improved finite volume analysi
Gasser-Leutwyler coefficients: A progress report
Last year, we reported our first results on the determination of
Gasser-Leutwyler coefficients using partially quenched lattice QCD with three
flavors of dynamical staggered quarks. We give an update on our progress in
determining two of these coefficients, including an exhaustive effort to
estimate all sources of systematic error. At this conference, we have heard
about algorithmic techniques to reduce staggered flavor symmetry breaking and a
method to incorporate staggered flavor breaking into the partially quenched
chiral Lagrangian. We comment on our plans to integrate these developments into
our ongoing program.Comment: 3 pages, 2 figures, Lattice2002(spectrum
Hadron Spectrum with Wilson fermions
We present results of a high statistics study of the quenched spectrum using
Wilson fermions at on lattices. We calculate the
masses of mesons and baryons composed of both degenerate and non-degenerate
quarks. Using non-degenerate quark combinations allows us to study baryon mass
splittings in detail. We find significant deviations from the lowest order
chiral expansion, deviations that are consistent with the expectations of
quenched chiral perturbation theory. We find that there is a
systematic error in the extracted value of , depending on the meson mass
ratio used to set its value. Using the largest estimate of we find that
the extrapolated octet mass-splittings are in agreement with the experimental
values, as is , while the decuplet splittings are 30% smaller
than experiment. Combining our results with data from the GF11 collaboration we
find considerable ambiguity in the extrapolation to the continuum limit. Our
preferred values are and , suggesting that the quenched approximation is good to only . We also analyze the discretization errors in heavy quark
masses.Comment: 52 pages. Tex. Modified "axis" source for figures also included.
Needs macro packages lanlmac and epsf. Uses hyperbasics if available.
Significant number of typographical errors correcte
The Kaon -parameter with Wilson Fermions
We calculate the kaon -parameter in quenched lattice QCD at
using Wilson fermions at and . We use two kinds of
non-local (``smeared'') sources for quark propagators to calculate the matrix
elements between states of definite momentum. The use of smeared sources yields
results with much smaller errors than obtained in previous calculations with
Wilson fermions. By combining results for and , we show that one can carry out the non-perturbative subtraction
necessary to remove the dominant lattice artifacts induced by the chiral
symmetry breaking term in the Wilson action. Our final results are in good
agreement with those obtained using staggered fermions. We also present results
for -parameters of the part of the electromagnetic penguin
operators, and preliminary results for \bk\ in the presence of two flavors of
dynamical quarks.Comment: 39 pages, including 9 PS figures (LA UR-91-3522
QCD with dynamical Wilson fermions
We present results from a study of QCD with two flavors of Wilson fermions using the hybrid Monte Carlo algorithm, which incorporates the effects of fermion loops exactly. We evaluate the performance of the algorithm and its potential for large-scale computations. We argue that in the best case the algorithm slows down as V^(5/4)mq^(-13/4) at a fixed gauge coupling. We present improved algorithms for calculating the inverse and the determinant of the Wilson fermion operator. Results for the finite-temperature transition on 4×6^3 and 6×8^3 lattices are presented at β=5.2-5.6. We also give Wilson loop expectation values obtained on 84 lattices at β=5.3 for six values of κ. The data show evidence for screening in the qq̅ potential. Lastly, on comparing Wilson and staggered-fermion results we find that β=5.3 is far from the scaling region