O(\alpha_s) corrections to the decays of polarized W^+- and Z bosons into massive quark pairs

TL;DR

This paper calculates the next-to-leading order QCD corrections to polarized W and Z boson decays into massive quark pairs, revealing significant finite mass effects and applying results to top quark decay and electron-positron collision processes.

Contribution

It provides the first detailed O(α_s) corrections to polarized decay functions of massive W and Z bosons, including second-order quark mass effects, with applications to top decay and e+e- processes.

Findings

Strong dependence of NLO decay functions on quark mass effects.

Quantitative results for helicity fractions in top decay.

Analysis of polarization effects in e+e- collisions.

Abstract

We present O(\alpha_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 \rho_{mm} of the W^+ boson followed by the polarized decay W^+(\uparrow) -> q_1 qbar_2 for which we determine the O(\alpha_s) polar angle decay distribution. We also discuss NLO polarization effects in the production/decay process e^+e^- -> Z(\uparrow) -> q qbar.