Download Free Nonlocal Condensates And Qcd Sum Rules For The Pion Form July 1991 Book in PDF and EPUB Free Download. You can read online Nonlocal Condensates And Qcd Sum Rules For The Pion Form July 1991 and write the review.

We extend the QCD sum rule analysis of the pion electromagnetic form factor F(sub)pi(Q^2) into the region of moderately large momentum transfers 3GeV^2
The authors investigate a model QCD sum rule for the pion wave function[var-phi][sub[pi]](x) based on the non-diagonal correlator whose perturbative spectral density vanishes and[Phi](x, M[sup 2]), the theoretical side of the sum rule, consists of condensate contributions only. They study the dependence of[Phi](x, M[sup 2]) on the Borel parameter M[sup 2] and observe that[Phi](x, M[sup 2]) has a humpy form, with the humps becoming more and more pronounced when M[sup 2] increases. They demonstrate that this phenomenon reflects just the oscillatory nature of the higher states wave functions, while the lowest state wave function, [var-phi][sub[pi]](x), extracted from their QCD sum rule analysis, has no humps, is rather narrow and its shape is close to the asymptotic form[var-phi][sub[pi]][sup as](x)= 6x(1[minus]x).
The QCD sum rule calculation of the pion wave function by Chernyak and Zhitnitsky is implicitly assuming that the correlation length of vacuum fluctuations is large compared to the typical hadronic scale ~ 1/m(sub)p, so that one can substitute the orginal nonlocal objects like (q-bar(0)q(z)) by constant (q-bar(0)q(0))-type values. We outline a formalism enabling one to work directly with the nonlocal condensates, and construct a modified sum rule for the moments (Xi^N) of the pion wave function. The results are rather sensitive to the value of the parameter lambda^2(sub)q = (q-barD^2q)/(q-bar q) specifying the average virtuality of the vacuum quarks. Varying it from the most popular value lambda^2(sub)q = 0.4 GeV^2 up to the value lamba^2(sub)q = 1.2 GeV^2 suggested by the instanton liquid model, we obtain (Xi^2) = 0.25 - 0.20, to be compared to the CZ value (Xi^2) = 0.43 obtained with lambda^2(sub)q = 0.
Within the QCD sum rule approach, we develop a formalism that enables one to calculate the form factors of the heavy-light mesons in the m{sub Q} --> (infinity) limit. It is shown that the behavior of the universal Isgur-Wise form factor is determined by the quark propagation function in imaginary time.