O(α _s ) corrections to the decays of polarized W ^± and Z bosons into massive quark pairs

Abstract

We present O(α _s ) results on the decays of polarized W ^± and Z bosons into massive quark pairs. The NLO QCD corrections to the polarized decay functions are given up to the second order in the quark mass expansion. We find a surprisingly strong dependence of the NLO polarized decay functions on finite quark mass effects even at the relatively large mass scale of the W ^± and Z bosons. As a main application we consider the decay t→b+W ⁺ involving the helicity fractions ρ _mm of the W ⁺ boson followed by the polarized decay $W^{+}(\uparrow)\to q_{1}\bar{q}_{2}$ for which we determine the O(α _s ) polar angle decay distribution. We also discuss NLO polarization effects in the production/decay process $e^{+}e^{-}\to Z(\uparrow)\to q\bar{q}$.