Related papers: Perturbative QCD and Tau Decay
The spin asymmetry parameter $A_\tau$ characterizing the angular distribution of the total hadron momentum in the decay of a polarized tau can be calculated rigorously using perturbative QCD and the operator product expansion. Perturbative…
We apply analytic perturbation theory to the inclusive decay of a $\tau$ lepton into hadrons. It is shown that the resulting analyticity of the coupling constant strongly influences the value of the QCD $\Lambda$-parameter extracted from…
We construct new tests of perturbative QCD by considering a hypothetical tau lepton of arbitrary mass, which decays hadronically through the electromagnetic current. We can explicitly compute its hadronic width ratio directly as an integral…
The total $\tau$ hadronic width can be accurately calculated using analyticity and the operator product expansion. The theoretical analysis of this observable is updated to include all available perturbative and non-perturbative…
In this paper a general method to measure the longitudinal polarization of $\tau$ lepton in the process $pp \rightarrow Z^{0} \rightarrow \tau\tau$ is described. The method of optimal observable allows to distinguish between the $\tau$…
Theoretical description of inclusive tau lepton hadronic decay is performed in the framework of Dispersive approach to QCD. The significance of effects due to hadronization is demonstrated. The approach on hand is capable of describing…
The inclusive tau lepton hadronic decay is studied within Dispersive approach to QCD. The significance of effects due to hadronization is convincingly demonstrated. The approach on hand proves to be capable of describing experimental data…
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…
The calculation of perturbative corrections to the spectral moments observable in hadronic $\tau$ decays is reconsidered. The exact order-$\alpha_s^3$ results and the resummation procedure of Le~Diberder and Pich are compared with a partial…
We analyze tau lepton decay observables, namely moments of the hadronic spectral density in the finite energy interval (0,M_\tau), within finite order perturbation theory including \alpha_s^4 corrections. The start of asymptotic growth of…
Semileptonic decays of polarised $\tau$ leptons are investigated. Predictions for the rate, based on CVC and chiral Lagrangians, are contrasted with experiments. Predictions for the angular distributions of three meson final states are…
The dispersive approach to QCD is applied to the study of the inclusive tau lepton hadronic decay. This approach provides the unified integral representations for the hadronic vacuum polarization function, related R function, and Adler…
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 represent a clean laboratory for the precise study of quantum chromodynamics (QCD). Observables (sum rules) based on the spectral functions of hadronic tau decays can be related to QCD quark-level calculations to…
The angular asymmetry in decays of polarized muons and tau leptons is discussed. Both the standard $V-A$ Fermi model and the general parameterization via Michel parameters are considered. Numerical importance of contributions suppressed by…
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…
We revisit the determination of alpha_s(m_tau) using a fit to inclusive tau hadronic spectral moments in light of (1) the recent calculation of the fourth-order perturbative coefficient K_4 in the expansion of the Adler function, (2) new…
The QCD analysis of hadronic tau decays is reviewed and a summary of the present phenomenological status is presented. The following topics are discussed: the determination of alpha_s(m_tau) = 0.338 +- 0.012 from the inclusive tau hadronic…
An updated measurement of alpha_s(m_tau) from ALEPH tau hadronic spectral functions is presented. We report a study of the perturbative prediction(s) showing that the fixed-order perturbation theory manifests convergence or principle…
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…