Related papers: Determination of alpha_s from tau decays
Double-pinched Borel-Laplace sum rules are applied to ALEPH $\tau$-decay data. For the leading-twist ($D=0$) Adler function a renormalon-motivated extension is used, and the 5-loop coefficient is taken to be $d_4=275 \pm 63$. Two $D=6$…
We elaborate on the relation between perturbative and power-like corrections to short-distance sensitive QCD observables. We confront theoretical expectations with explicit perturbative calculations existing in literature. As is expected,…
It is well known that in every experiment involving charged particles there are individual photons emitted with small energy /omega and those with /omega < /omega_{0} will not be detected but are present in the data. The typical procedure…
Analytic versions of QCD are those whose coupling alpha_s(Q^2) does not have the unphysical Landau singularities on the space-like axis (-q^2=Q^2 > 0). The coupling is analytic in the entire complex plane except the time-like axis (Q^2 <…
The `XIIIth Quark Confinement and the Hadron Spectrum' conference (Confinement 2018) contained a `Round Table Discussion' on the status of the determinations of the strong coupling $\alpha_s(m_Z)$ as well as prospects for future…
Using only independent high-scale OPE input, we investigate QCD sum rule constraints on two currently incompatible versions of the I=1 vector spectral function, one obtained from electroproduction data, the other from hadronic tau decay…
Coupled oscillator networks provide mathematical models for interacting periodic processes. If the coupling is weak, phase reduction -- the reduction of the dynamics onto an invariant torus -- captures the emergence of collective dynamical…
We present a new approach to determining the strong coupling $\alpha_s(Q)$, over the entire range of validity of perturbative QCD, for scales above $\Lambda_{\mathrm{QCD}}$ and up to the Planck scale $\sim1.22\cdot10^{19}$\,GeV, with the…
Inspired by the relation between the hadronic decay of the tau lepton and the electron-positron annihilation into hadrons, we derive new tests of perturbative QCD. We design a set of commensurate scale relations to test the self-consistency…
Hadronic $\tau$ decays are studied as probe of new physics. We determine the dependence of several inclusive and exclusive $\tau$ observables on the Wilson coefficients of the low-energy effective theory describing charged-current…
We consider the impact of O(alpha^2) hadronic corrections to the energy spectrum of the decay electron in muon decay. We find that the correction can be described, within good approximation, by a linear function in the electron energy.…
We describe how complications encountered in the extraction of V_us from flavor-breaking hadronic tau decay sum rules, in particular those associated with the slower than previously anticipated convergence of the relevant D=2 OPE series,…
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…
Hadronization in tau -> K K pi nu_tau decays is driven by both vector and axial-vector currents that we study, guided by the following principles: The 1/N_C expansion -worked out at leading order, considering only the contribution of the…
Corrections of order $\alpha_s^4$ for the axial singlet contributions for the decay rates of the $Z$-boson into hadrons are evaluated in the limit of the heavy top quark mass. Combined with recently finished ${\cal O}(\alpha_s^4)$…
A number of recent determinations of $m_s$ using hadronic $\tau$ decay data involve inclusive analyses based on the so-called $(k,0)$ spectral weights. We show here that the OPE representations of the longitudinal contributions appearing in…
The strong coupling $\alpha_s$ is extracted with high precision through fits to lattice-QCD data for the static energy. Our theoretical framework is based on R-improving the three-loop fixed-order prediction for the static energy: we remove…
Analytic formulae for the one-loop order QCD corrections to the differential width of the semileptonic b decay are given with the tau polarization taken into account. Thence the polarization of tau is expressed by its energy and the…
In the chiral limit, the $D=6$ contribution to the Operator Product Expansion (OPE) of the $\mathrm{VV-AA}$ correlator of quark currents only depends on two vacuum condensates, which can be related to hadronic matrix elements associated to…
We discuss the current use of the operator product expansion in QCD calculations. Treating the OPE as an expansion in inverse powers of an energy-squared variable (with possible exponential terms added), approximating the vacuum expectation…