Related papers: Perturbative relations between $e^+e^-$ annihilati…
Bose-Einstein correlations of identical charged-pion pairs produced in hadronic Z decays are analyzed in terms of various parametrizations. The tau-model with a one-sided L\'evy proper-time distribution provides a good description, enabling…
The recent results from Belle of the $\tau^-\to\nu_\tau\pi^-e^+e^-$ analysis has incentivated us to make a reanalysis of a former work where the Structure Dependent parts are obtained using Resonance Chiral Theory. Here we rely on the same…
We analyze inclusive $\tau$ decay using a modified version of the $a$ expansion, a non-perturbative technique in which the effective coupling is analytic in the infrared region. The modification involves renormalization group improvement of…
Next-to-next-to-leading contributions to the cross section sigma(e+e- -> tau+tau-) at energies close to threshold are analysed, taking into account the known non-relativistic effects and O(alpha^2) corrections. The numerical changes with…
We have studied the $\tau^-\to K^-\eta^{(\prime)}\nu_\tau$ decays within Chiral Perturbation Theory including resonances as explicit degrees of freedom. We have considered three different form factors according to treatment of final-state…
In a bottom-up approach we investigate lepton-flavour violating processes $\tau \to 3 \ell$ that are mediated by New Physics encoded in effective-theory operators of dimension six. While the opportunity to scrutinize the underlying operator…
A method for the resummation of nonalternating divergent perturbation series is described. The procedure constitutes a generalization of the Borel-Pad\'{e} method. Of crucial importance is a special integration contour in the complex plane.…
We study the effects of charged tensor weak currents on the strangeness-changing decays of the $\tau$ lepton. First, we use the available information on the $K^+_{e3}$ form factors to obtain BR$(\tau^- \rightarrow K^-\pi^0 \nu_{\tau})\sim…
The hadronic decay rate of the tau lepton serves as one of the most precise determinations of the QCD coupling alpha_s. The dominant theoretical source of uncertainty at present resides in the seeming disparity of two approaches to…
The renormalization group relations for the higher-order hadronic vacuum polarization function perturbative expansion coefficients are studied. The folded recurrent and unfolded explicit forms of such relations are obtained. The explicit…
We use a new compilation of the hadronic $R$-ratio from available data for the process $e^+e^-\to$ hadrons below the charm mass to determine the strong coupling $\alpha_s$, using finite-energy sum rules. Quoting our results at the $\tau$…
We present the first measurements of branching fractions of rare tau-lepton decays, $\tau^- \rightarrow \pi^- \nu_{\tau} \ell^+ \ell^-$ ($\ell = e$ or $\mu$), using a data sample corresponding to 562 fb$^{-1}$ collected at a center-of-mass…
Using the massive helicity formalism we calculate the five-body average square amplitude of the decays $\tau^{-}\to \ell_i^{-} \ell_i^{+} \ell_j^{-} \bar{\nu}_{j} \nu_{\tau}$ $(\ell=e,\,\mu)$ within the Standard Model (SM), we then…
In a small window of phase space, chiral perturbation theory can be used to make standard model predictions for tau decays into two and three pions. For $\tau \to 2\pi \nu_\tau$, we give the analytical result for the relevant form factor…
Estimates of higher-order contributions for perturbative series in QCD, in view of their asymptotic nature, are delicate, though indispensable for a reliable error assessment in phenomenological applications. In this work, the Adler…
In these lectures we give a concise introduction to the ideas of renormalon calculus in QED and QCD. We focus in particular on the example of the Adler D function of vacuum polarization, and on relations between perturbative renormalon…
The relation between the degree of entanglement and time scale of time-irreversible behavior is investigated for classically chaotic quantum coupled kicked rotors by comparing the entanglement entropy (EE) and the lifetime of correspondence…
Two and three point functions of composite operators are analysed with regard to (logarithmically) divergent contact terms. Using the renormalisation group of dimensional regularisation it is established that the divergences are governed by…
The process $e^- e^+ \to \tau^- \tau^+$ is of particular interest because the tau lepton polarisation can be reconstructed, allowing its chiral nature to be probed. This note reports on a study of the reconstruction of the di-tau final…
In this talk, we consider the computation of D and B fragmentation functions in e+e- annihilation. We present an improved differential cross section that merges together the O(alpha_s^2) fixed-order calculation and the…