Talk presented by Paul Rakow

Parallel Session: Improvement and Renormalization II

Tuesday June 29th, 18.00 - 18.20, Room B

Operator improvement and renormalization for clover fermions

Abstract: As is well known improvement of the action is sufficient to give improved masses, but to get improved matrix elements we need to improve the operator too, by adding irrelevant terms with higher dimension. We have carried out 1-loop lattice perturbation theory calculations for quark bilinear operators in the clover action, with an arbitrary value of the clover coupling constant $c_{SW}$ and quark mass. We show that, when the clover coupling is correctly chosen, all $O(a)$ discretization errors can be removed, despite the extremely complicated form of the answer with arbitrary mass. Equations of motion give us some freedom to vary the improvement coefficients. We can always find one set of improvement coefficients for which operator Green's functions are free of contact terms, leading to offshell improvement of Green's functions.

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