Methodologies Of QCD Sum Rules And Their Applications To Light Hadronic States

QCD sum rules (QCDSR) is an semi-analytic non-perturbative method, of which the key element, the QCD correlator, connects the theory of the quark level with the phenomenology of the hadronic level via the dispersion relation. The poorly understood non-peturvative effects are absorbed in a series of vaccum condensates which can be determined phenomenologically.Therefore, QCDSR can be thought of as integration of three aspects (levels): QCD(?) sum-rule methodology(?)hadronic phenomenology. Our research involves these three aspects (levels).On the aspect of QCD calculation, we explicitly study the higher power corrections (dimension-8 quark and gluon condensate terms) to the (1-+,0++) correlation function with consideration of the mixing between the quark and gluon operators under renormalization. We study the influence of these higher dimensional condensates on the OPE convergence and the sum-rule mass deter-ination. Besides, we also examine the calculation of the next-to-leading order terms of(?sG2)and <mqqq> in the correlator of the vector current. We especially study the effects of these terms in determining the Holder-inequality-determined sum rule window.On the aspect of the sum-rule methodology, we use (and try to improve some of) the differ-ent sum rules, including Laplace/Borel sum rules, finite energy sum rules, Monte-carlo based sum rules etc. We introduce the stability criteria developed in traditional QCD sum rules in the appli-cation of the light-cone QCD sum rules. We also improve the Monte-Carlo based QCD sum rules by introducing the rigourous Holder-inequality-determined sum-rule window and a Breit-Wigner type parametrization (involving the hadronic width) for the phenomenological spectral function,allowing predictions without assumptions on the sum-rule window.On the aspect of the hadronic phenomenology, we obtain predictions for the mass and partial decay widths of (some decay patterns) of the 1-+ light hybrid meson, the masses of the 0-- and 1+- four-quark states. Our results on the 1-+ light hybrid suggest ?1(2015) is the most likely one among the existing hybrid candidates and ?1??? may be an important decay mode in identifying the 1-+ light hybrid state. Our study of the 0-- four-quark state suggest the ?? dominance in the D0 decay may be a four-quark state and ?0? is the only possible S-wave decay mode and therefore worth special attention experimentally. Our predictions for the mass of the 1+- four-quark state suggest such a state lie within the 270 MeV range above the conventional qq state h1(1170).