NEW QCD SUM-RULES FOR NUCLEON AXIAL-VECTOR COUPLING-CONSTANTS

Two new sets of QCD sum rules for the nucleon axial-vector coupling co nstants are derived using the external-field technique and generalized interpolating fields. An in-depth study of the predicative ability of these sum rules is carried out using a Monte Carlo-based uncertainty analysis. The results show that the standard implementation of the QCD sum rule method has only marginal predicative power Tor the nucleon a xial-vector coupling constants, as the relative errors are large. The errors range from approximately 50% to 100% compared to the nucleon ma ss obtained from the same method, which has only a 10%-25% error. The origin of the large errors is examined. Previous analyses of these cou pling constants are based on sum rules that have poor operator product expansion convergence and large continuum contributions, Preferred su m rules are identified and their predictions are obtained. We also inv estigate the new sum rules with an alternative treatment of the proble matic transitions which are not exponentially suppressed in the standa rd treatment. The alternative treatment provides exponential suppressi on of their contributions relative to the ground state. Implications f or other nucleon current matrix elements are also discussed.