Calculation of power corrections to hadronic event shapes

Abstract

We compute power corrections to hadronic event shapes in e + e − annihilation, assuming an infrared regular behaviour of the effective coupling α S . With the integral of α S over the infrared region as the only non-perturbative parameter, also measured in heavy quark physics, we can account for the empirical features of 1/Q corrections to the mean values of various event shapes.

Event shapes in e+e annihilation and deep inelastic scattering

“…This was proposed and investigated in [130], § and the combination C V P is the same that appears in the power correction for the mean value [128], discussed in section 4. Eq.…”

The Strong Coupling Constant

“…[62] This dependence on phenomenological models introduces an additional "hadronization uncertainty" into an α smeasurement. Only recently analytic calculations [63] became available, based on the study of the long-distance behaviour of leading order matrix elements, which in some respect can be understood as generalizations of the OPE. Identifying different classes of power-law corrections, they introduce a small number of universal parameters, e.g.…”

QCD studies in e+e− annihilation from 30 GeV to 189 GeV

“…The energy dependence of moments of the event shape variables has been described [11] as a sum of the perturbative contributions and a power law dependence due to non-perturbative contributions. The first moment of an event shape variable f is written as…”

“…and a takes a value 1 for B T and 2 for B W and α CMW is related to α s [11]. We have carried out fits to the first moments of the five event shape variables separately with α s (m Z ) and α 0 as free parameters.…”

“…The perturbative and non-perturbative QCD contributions are obtained from a fit using the power correction formula [11]. This approach was first applied by the DELPHI collaboration [12].…”