Renormalization scheme dependence in e+e− annihilation and τ-lepton decay at the next-to-next-to-leading order of perturbative QCD

Abstract

We present a detailed investigation of the renormalization scheme dependence of the next-to-next-to-leading order QCD predictions for the processes e+e-~hadrons and x-* v,+hadrons. Based on it the comparison of the results obtained in three frequently used approaches to resolving the renormalization scheme ambiguities with experimental data is carried out.

Renormalization scheme dependence in analytic approach to perturbative QCD

“…1, we plot the QCD correction r(s) as a function of √ s/Λ MS for these two schemes in usual treatment, as it was considered, e.g., in Refs. [4,12,13] and within the AA. One can see that the analytically improved result for R(s) obeys a stable behaviour for the whole interval of energies being practically scheme independent.…”

ESTIMATES OF THE HIGHER ORDER QCD CORRECTIONS TO R(s), Rτ AND DEEP INELASTIC SCATTERING SUM RULES

“…The foundations of Ref. [11] were further improved in the process of phenomenological studies of the QCD predictions for R τ , using the explicite separations of the expressions for the n-th order coefficients r τ n to the n-th order coefficients d n of the Euclidean D-function and the certain contributions, which can be explicitely taken into account after completing the calculations in the k ≤ n − 1 order of the perturbation theory [12].…”

All-orders infrared freezing of Re+e− in perturbative QCD

“…These predictions were then smeared using the technique of Poggio-Quinn-Weinberg (PQW) [5], and were in suprisingly good agreement with similarly smeared experimental data for R e + e − . Some scepticism about the existence of infra-red fixed point behaviour had previously been expressed [6]. In this letter we wish to demonstrate that including allorders in perturbation theory the perturbative corrections to R e + e − do freeze in the infra-red.…”