Improved test of the flavor independence of strong interactions

Abstract

We present an improved comparison of the strong coupling of the gluon to light ${(q}_{l}=u+d+s),$ c, and b quarks, determined from multijet rates in flavor-tagged samples of hadronic ${Z}^{0}$ decays recorded with the SLC Large Detector at the SLAC Linear Collider between 1993 and 1995. Flavor separation among primary ${q}_{l}{q}_{l},$ $c\overline{c},$ and $b\overline{b}$ final states was made on the basis of the reconstructed mass of long-lived heavy-hadron decay vertices, yielding tags with high purity and low bias against \ensuremath{\geqslant} 3-jet final states. We find: ${\ensuremath{\alpha}}_{s}^{c}/{\ensuremath{\alpha}}_{s}^{\mathrm{uds}}={1.036\ifmmode\pm\else\textpm\fi{}0.043(\mathrm{stat})}_{\mathrm{\ensuremath{-}}0.045}^{+0.041}{(\mathrm{syst})}_{\mathrm{\ensuremath{-}}0.018}^{+0.020}(\mathrm{theory})$ and ${\ensuremath{\alpha}}_{s}^{b}/{\ensuremath{\alpha}}_{s}^{\mathrm{uds}}={1.004\ifmmode\pm\else\textpm\fi{}0.018(\mathrm{stat})}_{\mathrm{\ensuremath{-}}0.031}^{+0.026}{(\mathrm{syst})}_{\mathrm{\ensuremath{-}}0.029}^{+0.018}(\mathrm{theory}).$