标题： TO_BE_TRANSLATED: Mixed quark-gluon condensate from instantons 显示英文标题

标题： Mixed quark-gluon condensate from instantons

摘要： TO_BE_TRANSLATED: We calculate the vacuum expectation value of the dimension-5 "mixed" quark-gluon operator, $O_\sigma = \bar\psi (\lambda^a /2) \sigma_{\mu\nu} \psi F_{\mu\nu}^a$, in the instanton vacuum. Within the $1/N_c$--expansion the QCD operator is replaced by an effective many-fermion operator, which is averaged over the effective theory of massive quarks derived from instantons. We find $m_0^2 \equiv \langle O_\sigma \rangle / \langle \bar\psi\psi \rangle \approx 4 \bar\rho^{-2} = 1.4 GeV^2$, somewhat larger than the estimate from QCD sum rules for the nucleon. 显示英文摘要

摘要： We calculate the vacuum expectation value of the dimension-5 "mixed" quark-gluon operator, $O_\sigma = \bar\psi (\lambda^a /2) \sigma_{\mu\nu} \psi F_{\mu\nu}^a$, in the instanton vacuum. Within the $1/N_c$--expansion the QCD operator is replaced by an effective many-fermion operator, which is averaged over the effective theory of massive quarks derived from instantons. We find $m_0^2 \equiv \langle O_\sigma \rangle / \langle \bar\psi\psi \rangle \approx 4 \bar\rho^{-2} = 1.4 GeV^2$, somewhat larger than the estimate from QCD sum rules for the nucleon.