The SVZ-Expansion and Beyond
Abstract
Description
I discuss the standard SVZ-expansion of the QCD two-point correlators in terms of the QCD vacuum condensates and beyond it due to a new unflavoured 1/Q^2-term (tachyonic gluon mass squared λ^2) which modelizes the effects of uncalculated higher order perturbative terms. The approach is confronted with low-energy and lattice data. One can notice that, in the different examples studied here, high-dimension condensates are expected to deviate largely from their vacuum saturation (large N_c) values, while the new 1/Q^2-term due to λ^2 solves the hadronic mass scale hierarchy-puzzle encountered in the early SVZ-sum rule analysis and improves the low-energy phenomenology. From tau-decay data, one can extract the running strange quark mass m_s(2 GeV)=(93^{+29}_{-32}) MeV and a more accurate value of the QCD coupling α_s(M_Z)=0.117+- 0.002.
7 pages in 2-column format, 1 figure, 4 tables, Talk given at the Workshop Understanding Confinement (Ringberg Castle, 16-21th May 2005) and at QCD 05 International Conference (Montpellier, 4-8th July 2005)
7 pages in 2-column format, 1 figure, 4 tables, Talk given at the Workshop Understanding Confinement (Ringberg Castle, 16-21th May 2005) and at QCD 05 International Conference (Montpellier, 4-8th July 2005)