State-of-the-Art Predictions for C-parameter and a Determination of alpha_s

TL;DR

This paper advances the theoretical prediction of the C-parameter distribution in e+e- annihilation by achieving N3LL resummation, incorporating nonperturbative corrections, and extracting a precise value of alpha_s(mZ).

Contribution

It provides the first N3LL resummed prediction for the C-parameter distribution including nonperturbative effects and determines alpha_s with high precision from experimental data.

Findings

Achieved N3LL resummation accuracy for the C-parameter distribution.

Extracted alpha_s(mZ) = 0.1123 ± 0.0015 from data.

Incorporated nonperturbative power corrections and addressed renormalon ambiguities.

Abstract

The C-parameter event-shape distribution for e+e- annihilation into hadrons is computed in the framework of SCET including input from fixed-order perturbation theory. We calculate all missing ingredients for achieving N3LL resummation accuracy in the cross section, which is then matched onto O(alpha_s^3) fixed-order results. Hadronization power corrections are incorporated as a convolution with a nonperturbative shape function. Wide-angle soft radiation effects introduce an O(Lambda_QCD) renormalon ambiguity in the cross section, which we cure by switching to the Rgap short-distance scheme. We also include hadron mass effects, but find their effect is rather small. Performing fits to the tail of the C-parameter distribution for many center of mass energies we find that the strong coupling constant is alpha_s(mZ) = 0.1123 +-0.0015, with chi^2/dof=0.99.