Related papers: QCD vacuum condensates from tau-lepton decay data
We present a new framework for the extraction of the strong coupling from hadronic \tau decays through finite-energy sum rules. Our focus is on the small, but still significant non-perturbative effects that, in principle, affect both the…
An exhaustive number of QCD finite energy sum rules for $\tau$-decay together with the latest updated ALEPH data is used to test the assumption of global duality. Typical checks are the absence of the dimension $d=2$ condensate, the…
Basic chiral QCD parameters (the pion decay constant, the quark and gluon condensates, the dynamically generated quark mass, etc) as well as the vacuum energy density (up to the sign, by definition, the bag constant) have been calculated…
The spectral function $\rho_{V-A}(s)$ is determined from ALEPH and OPAL data on hadronic tau decays using a neural network parametrization trained to retain the full experimental information on errors, their correlations and chiral sum…
In this article, we calculate the contributions of the vacuum condensates up to dimension-6 including the $\mathcal{O}(\alpha_s)$ corrections to the quark condensates in the operator product expansion, then study the masses and decay…
Utilizing the in-medium Lorentz decomposition of operators generating QCD condensates we derive general constraints among the latter ones by the requirement of a smooth transition from medium to vacuum. In this way we relate the vacuum…
Precision tests of QCD perturbation theory are not readily available from experimental data. The main reasons are systematic uncertainties due to the confinement of quarks and gluons, as well as kinematical constraints which limit the…
2-point correlators of vector and axial currents, obtained from tau-decay data, are studied within the framework of perturbative QCD and Operator Product Expansion. Various sum rules, obtained from Borel transformation of the correlators in…
A visible improvement of the QCD sum-rule framework, achieved only recently by a slightly more sophisticated consideration of the hadron excitations and continuum, is applied to the extraction of the decay constants of heavy-light…
The finite energy sum rule extraction of the strong coupling {\alpha}_s from hadronic {\tau} decay data provides one of its most precise experimental determinations. As precision improves, small non-perturbative effects become increasingly…
In the limit of an infinite number of colors, an analytic expression for the quark condensate in $QCD_{1+1}$ is derived as a function of the quark mass and the gauge coupling constant. For zero quark mass, a nonvanishing quark condensate is…
The operator product expansion (OPE) for the difference of vector and axial current correlators is analyzed for complex values of momentum q^2. The vector and axial spectral functions, taken from hadronic tau-decay data, are treated with…
We present new results of the tau hadronic spectral function analysis using data accumulated by the ALEPH detector at LEP during the years 1991-94. In addition to the vector spectral functions, the axial-vector spectral functions and,…
We review the recent status of the QCD sum rule approach to study the properties of hadrons in vacuum and in hot or dense matter. Special focus is laid on the progress made in the evaluation of the QCD condensates, which are the input of…
Hadronic tau decays offer the possibility of determining the strong coupling alpha_s at relatively low energy. Precisely for this reason, however, good control over the perturbative QCD corrections, the non-perturbative condensate…
We present a determination of the perturbative QCD (pQCD) coupling using the V+A channel ALEPH $\tau$-decay data. The determination involves the double-pinched Borel-Laplace Sum Rules and Finite Energy Sum Rules. The theoretical basis is…
A recently proposed scheme is used to saturate the spectral side of the QCD sum rules derived from the thermal, two-point correlation functions of the vector and the axial-vector currents. At low temperature, it constructs the spectral…
We use ALEPH data on hadronic $\tau$ decays in order to calculate Euclidean coordinate space correlation functions in the vector and axial-vector channels. The linear combination $V-A$ receives no perturbative contribution and is…
We apply a recently constructed model of analytic QCD in the Operator Product Expansion (OPE) analysis of the tau lepton decay data in the V+A channel. The model has the running coupling A(Q^2) with no unphysical singularities, i.e., it is…
The next-to-next-to-leading order perturbative QCD corrections to R_tau and the higher moments of the invariant mass distribution in the hadronic tau decays are considered. The renormalization scheme dependence of these corrections is…