Study Of Quantum Chromodynamics Sum Rule For 0^-+ Pseudoscalar Glueball Correlation Function

Based on the correction from instanton-gluon interference to correlation function, the properties of the 0-+ pseudoscalar glueball is investigated by families of Laplace sum rules and Gaussian ones in this thesis.In the framework of semiclassical expansion for quantum chromodynamics (QCD) in the instanton liquid background, the contribution arising from the interfer-ence between instantons and the quantum gluon fields is calculated, and included in the correlation function together with the pure-classical contribution from instantons and the perturbative one. The interference contribution is turned to be gauge-invariant, free of infrared divergence, and plays a great role to restore the positivity of the spectra of the full correlation function. The effect of the contribution of topological charge screening is found to be negligible as comparing with the interference one in the con-sidered energy region, and the correlation function is already positive with including the interference contribution. So, the topological charge screening contribution is ex-cluded from the 0-+ pseudoscalar glueball correlation function in our work. On the other hand, the negligible contribution from vacuum condensates is excluded in our correlation function too, to avoid the double counting. In fact, the condensate contri-butions turns out to be very small as compared with those of instantons in the glueball channels, and may be understood as a small fraction of the corresponding instanton one in the local limit.For the spectral function of the finite-width resonances, instead of the usual zero-width approximation for the resonances, the usual Breit-Wigner form with a suit-able threshold behavior is adopted. To face a more realistic phenomenological situ-ation, we adopt the five-resonances model which include the resonances below and near the ?(1405) into the finite-width spectral function.Finally, the values of the mass, decay width and coupling constants for the 0-+ resonance are obtained by inputting a few of standard QCD parameters. A consistency between the subtracted and unsubtracted sum rules is very well justified in each family of sum rules. And our results of Laplace sum rules and the Gaussian sum rules are con-sistent with each other as well. It demonstrates that ?(1405) is a good candidate for the lowest 0-+ pseudoscalar glueball with some mixture with the nearby excited isovector and isoscalar qq mesons. This is a first theoretical support for the phenomenological estimation from the sum rule approach.