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The SVZ-Expansion and Beyond

Stephan Narison
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Abstract

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.

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Stephan Narison. 2005-08-24. The SVZ-Expansion and Beyond. https://arxiv.org/abs/hep-ph/0508259

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