Expectation values of four-quark operators in pions
Abstract
The values of four-quark operators averaged over pions are expressed through those averaged over vacuum. The specific values are obtained in the framework of the factorization assumption. For the condensates of the light quarks of the same flavour q q q q the scalar condensate is shown to be an order of magnitude larger than the other ones. The condensates containing the strange quarks q q s s appear to be only about twice smaller than those of the light quarks. The degeneracy of the ground state in the Nambu--Jona--Lasinio model is shown explicitly.
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