Assessing the sensitivity of Energy-Energy Correlations in $e^+e^-$ annihilation to TMD dynamics

TL;DR

This paper investigates the potential of energy-energy correlations in electron-positron annihilation to inform about TMD dynamics, but finds current data insufficient for meaningful constraints on key parameters.

Contribution

It provides a comprehensive N$^4$LL analysis of EEC in $e^+e^-$ annihilation and challenges previous claims about data constraints on TMD parameters.

Findings

Current data do not constrain the Collins-Soper kernel.

No meaningful constraints on the strong coupling constant $\

Abstract

We critically examine the back-to-back limit of the energy-energy correlation (EEC) in $e^+e^-$ annihilation as a potential source of information on the Collins-Soper kernel and the strong coupling constant. The analysis is performed within the framework of transverse momentum dependent (TMD) factorization at next-to-next-to-next-to-next-to-leading logarithmic (N$^4$LL) accuracy, using a global fit to all available experimental data. Contrary to previous claims, we demonstrate that the current data do not provide meaningful constraints on either the Collins-Soper kernel or $\alpha_s$.