Staggered fermion matrix elements using smeared operators
نویسندگان
چکیده
We investigate the use of two kinds of staggered fermion operators, smeared and unsmeared. The smeared operators extend over a 44 hypercube, and tend to have smaller perturbative corrections than the corresponding unsmeared operators. We use these operators to calculate kaon weak matrix elements on quenched ensembles at β = 6.0, 6.2 and 6.4. Extrapolating to the continuum limit, we find BK(NDR, 2 GeV) = 0.62 ± 0.02(stat)± 0.02(syst). The systematic error is dominated by the uncertainty in the matching between lattice and continuum operators due to the truncation of perturbation theory at one-loop. We do not include any estimate of the errors due to quenching or to the use of degenerate s and d quarks. For the ∆I = 3/2 electromagnetic penguin operators we find B (3/2) 7 = 0.62±0.03±0.06 and B (3/2) 8 = 0.77±0.04±0.04. We also use the ratio of unsmeared to smeared operators to make a partially non-perturbative estimate of the renormalization of the quark mass for staggered fermions. We find that tadpole improved perturbation theory works well if the coupling is chosen to be αMS(q ∗ = 1/a). (submitted to Physical Review D)
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