PARITY-VIOLATING NUCLEAR-FORCE AND QCD SUM-RULES

It is known that the method of QCD sum rules provides an efficient way for unraveling consequences of QCD for a physical process which invol ves strong interactions. Owing to modifications due to strong interact ions, on the other hand, nonleptonic weak interactions remain as a poo rly understood sector in the standard model. Thus, we have launched se rious efforts to use QCD sum rules to determine weak parity-violating nuclear forces, a flavor-conserving sector of nonleptonic weak interac tions which has been subject to experimental studies because of its pa rity-violating signature. As an illustrative example, I describe the p rocedure(3) of using QCD sum rules to obtain the weak parity-violating (p.v.) pion-nucleon coupling constant f(phi NN). We find that the res ult on f(pi NN) is consistent with the experimental upper limit found from F-18 parity-violating measurements. The method which we have adop ted is being used to determine the p.v. rho NN and omega NN couplings, which together with the weak pi NN coupling give rise to the parity-v iolating nuclear forces. It is also being used to study two-body weak decays of hyperons in order to shed some light on the empirical rules such as the Delta I = 1/2 rule.