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Hadronic decays of the $\tau$ lepton provide a clean environment to study hadron dynamics in an energy regime dominated by resonances, with the interesting information captured in the spectral functions. Recent results from ALEPH on…
The spectral functions of the vector current and the axial-vector current have been measured in hadronic tau decays using the OPAL detector at LEP. Within the framework of the Operator Product Expansion a simultaneous determination of the…
I report on some recent work done in collaboration with Santi Peris and Boris Phily (hep-ph/0007338) where, using the Aleph data on vector and axial-vector spectral functions, we test simple duality properties of QCD in the large-Nc limit…
The aim of this paper is to study the global existence of solutions to a coupled wave-Klein-Gordon system in space dimension two when initial data are small, smooth and mildly decaying at infinity. Some physical models strictly related to…
We present an update of the measurement of alpha_s(m_tau) from ALEPH tau hadronic spectral functions. We report a study of the perturbative prediction(s) showing that the fixed-order perturbation theory manifests convergence problems not…
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…
Experimental data on the total cross section of $e^+ e^-$ annihilation into hadrons are confronted with QCD and the operator product expansion using finite energy sum rules. Specifically, the power corrections in the operator product…
Motivated by recent work on three-point QCD sum rules in heavy quark physics, we use the simple quantum mechanical models to study the basic issue of duality in three-point sum rules. We show that while in all of these models the duality in…
Hadronic tau decay data provides access to the light quark vector (V) and axial vector (A) spectral functions. This makes possible investigations of the dynamics of QCD at intermediate scales and improved determinations of certain…
Three important QCD-related aspects of the $\tau$ and $\mu$ dynamics are reviewed: the determination of the strong coupling from the hadronic tau decay width, leading to the updated value $\alpha_s(m_\tau^2) = 0.331 \pm 0.013$; the…
Utilizing in-medium vector spectral functions which describe dilepton data in ultra-relativistic heavy-ion collisions, we conduct a comprehensive evaluation of QCD and Weinberg sum rules at finite temperature. The starting point is our…
The formation of codimension-one interfaces for multi-well gradient-driven problems is well-known and established in the scalar case, where the equation is often referred to as the Allen-Cahn equation. The proofs rely for a large on a…
Recently, we extracted the strong coupling, $\alpha_s(m_\tau^2)$, from the revised ALEPH data for non-strange hadronic tau decays. Our analysis is based on a method previously used for the determination of the strong coupling from OPAL…
An update of the ALEPH non-strange spectral functions from hadronic $\tau$ decays is presented. Compared to the 2005 ALEPH publication, the main improvement is related to the use of a new method to unfold the measured mass spectra from…
We review the determinations of the QCD coupling $\alpha_s$ from the inclusive and exclusive modes of $\tau$-decays. The most recent $\tau$-data provide the average value $ \alpha_ s \left(M^2_\tau \right)\simeq 0.347\pm 0.030 $…
Inclusive electron-proton and electron-deuteron inelastic cross sections have been measured at Jefferson Lab (JLab) in the resonance region, at large Bjorken x, up to 0.92, and four-momentum transfer squared Q2 up to 7.5 GeV2 in the…
It has been shown in recent analyses by ALEPH [1] and OPAL [2] that precision QCD tests are possible with hadronic tau decays by comparing spectral moments of the hadronic decay ratio of the tau with QCD calculations. In principle e+e- data…
We determined the NLO chiral low-energy constant $L_{10}$, and various combinations of NNLO chiral low-energy constants employing recently revised ALEPH results for the non-strange vector (V) and axial-vector (A) hadronic tau decay…
We present complete O(alpha_s^2) corrections to the decay b-->c+l+nu at the point where the invariant mass of the leptons sqrt{q^2} equals the c quark mass. We use this result, together with previously obtained corrections at the ends of…
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…