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

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 ${\alpha }_s$.

Comments: 25 pages, 11 figures