Hadronization effects in event shape moments

TL;DR

This paper combines NNLO perturbative QCD with a dispersive model for non-perturbative effects to analyze event shape moments in electron-positron annihilation, leading to a new precise determination of the strong coupling constant.

Contribution

It extends the dispersive model to match NNLO predictions and provides a more accurate extraction of ppa_s(M_Z) from experimental data.

Findings

ppa_s(M_Z)=0.1153 b1 0.0017 (exp) b1 0.0023 (th)

ppa_0=0.5132 b1 0.0115 (exp) b1 0.0381 (th)

Power corrections are larger than those from hadronization models in event generators.

Abstract

We study the moments of hadronic event shapes in $e^+e^-$ annihilation within the context of next-to-next-to-leading order (NNLO) perturbative QCD predictions combined with non-perturbative power corrections in the dispersive model. This model is extended to match upon the NNLO perturbative prediction. The resulting theoretical expression has been compared to experimental data from JADE and OPAL, and a new value for $\alpha_s(M_Z)$ has been determined, as well as of the average coupling $\alpha_0$ in the non-perturbative region below $\mu_I=2$ GeV within the dispersive model: \alpha_s(M_Z)&=0.1153\pm0.0017(\mathrm{exp})\pm0.0023(\mathrm{th}),\alpha_0&=0.5132\pm0.0115(\mathrm{exp})\pm0.0381(\mathrm{th}), The precision of the $\alpha_s(M_Z)$ value has been improved in comparison to the previously available next-to-leading order analysis. We observe that the resulting power corrections are considerably larger than those estimated from hadronization models in multi-purpose event generator programs.