Extraction of alpha_s from radiative Upsilon(1S) decays

TL;DR

Problem: extracting alpha_s from radiative Upsilon(1S) decays is sensitive to color-octet NRQCD effects and potential model dependence. Approach: the authors perform two independent extractions (lattice-based and continuum-based) using updated NRQCD color-octet matrix elements and CLEO data for R_gamma, avoiding model extrapolations. Findings: they obtain alpha_s(M_Upsilon(1S)) around 0.183–0.185 and alpha_s(MZ) around 0.119–0.120 with ~6% uncertainties, in good agreement with the PDG average. Significance: this work provides a competitive, model-independent determination of alpha_s from heavy quarkonium radiative decays and highlights the importance of color-octet contributions in the extraction.

Abstract

We improve on a recent determination of alpha_s from Gamma(Upsilon(1S)-->X gamma)/Gamma(Upsilon(1S)-->X) with CLEO data by taking into account color octet contributions and avoiding any model dependence in the extraction. We obtain alpha_s(M_Upsilon(1S))= 0.184+0.015-0.014, which corresponds to alpha_s(M_Z)=0.119+0.006-0.005.