Perturbative Improvement for Lattice QCD: An Update

Recent developments in the Symanzik improvement program for lattice QCD are reviewed.Comment: Invited talk at the workshop on "Lattice QCD on Parallel Computers" (Tsukuba, March 1997). One file producing 12 pages; LaTe

Mass renormalisation for improved staggered quarks

Improved staggered quark actions are designed to suppress flavour changing strong interactions. We discuss the perturbation theory for this type of actions and show the improvements to reduce the quark mass renormalisation compared to naive staggered quarks. The renormalisations are of similar size as for Wilson quarks.Comment: LaTeX, 3 pages, Lattice2001(spectrum

Mean link versus average plaquette tadpoles in lattice NRQCD

We compare mean-link and average plaquette tadpole renormalization schemes in the context of the quarkonium hyperfine splittings in lattice NRQCD. Simulations are done for the three quarkonium systems $c\bar c$, $b\bar c$, and $b\bar b$. The hyperfine splittings are computed both at leading and at next-to-leading order in the relativistic expansion. Results are obtained at a large number of lattice spacings. A number of features emerge, all of which favor tadpole renormalization using mean links. This includes much better scaling of the hyperfine splittings in the three quarkonium systems. We also find that relativistic corrections to the spin splittings are smaller with mean-link tadpoles, particularly for the $c\bar c$ and $b\bar c$ systems. We also see signs of a breakdown in the NRQCD expansion when the bare quark mass falls below about one in lattice units (with the bare quark masses turning out to be much larger with mean-link tadpoles).Comment: LATTICE(heavyqk) 3 pages, 2 figure

Highly Improved Naive and Staggered Fermions

We present a new action for highly improved staggered fermions. We show that perturbative calculations for the new action are well-behaved where those of the conventional staggered action are badly behaved. We discuss the effects of the new terms in controlling flavor mixing, and discuss the design of operators for the action.Comment: Contribution to Lattice2001(improvement); 3 page

Nonperturbative ``Lattice Perturbation Theory''

We discuss a program for replacing standard perturbative methods with Monte Carlo simulations in short distance lattice gauge theory calculations.Comment: 3 pages, uuencoded Latex file, two embedded figures and .sty file include

Moving NRQCD for B Form Factors at High Recoil

We derive the continuum and lattice tree-level moving NRQCD (mNRQCD) through order 1/m^2. mNRQCD is a generalization of NRQCD for dealing with hadrons with nonzero velocity u_mu. The quark's total momentum is written as P^mu=Mu^mu+k^mu where k^mu << Mu^mu is discretized and Mu^mu is treated exactly. Radiative corrections to couplings on the lattice are discussed. mNRQCD is particularly useful for calculating B->pi and B->D form factors since errors are similar at low and high recoil.Comment: 3 pages, 1 figure, Lattice2002(heavyquark