Determination of pion-baryon coupling constants from QCD sum rules
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We evaluate the pi-N-N, pi-Sigma-Sigma and pi-Sigma-Lambda coupling constants using QCD sum rules based on pion-to-vacuum matrix elements of correlators of two interpolating baryon fields. The parts of the correlators with Dirac structure k-slash gamma_5 are used, keeping all terms up to dimension 5 in the OPE and including continuum contributions on the phenomenological side. The ratios of these sum rules to baryon mass sum rules yield stable results with values for the couplings of g_{pi NN}=12+/-5, g_{pi Sigma Sigma}=7+/-4 and g_{pi Sigma Lambda}=6+/-3. The sources of uncertainty are discussed.
20 pages (RevTeX), 1 figure (attached). Revised version with corrected form for Y2 piece of hyperon correlators; numerical results differ from previous version
20 pages (RevTeX), 1 figure (attached). Revised version with corrected form for Y2 piece of hyperon correlators; numerical results differ from previous version