Speaker
Description
We present the first complete QCD corrections to both the inclusive decay width $\Gamma_t$, $W$-helicity fractions and semi-inclusive distributions for the top-quark decay process to the third order in the strong coupling constant $\alpha_s$, accomplished through a very efficient approach readily to be employed in many more related applications. We find, in particular, that the pure $\mathcal{O}(\alpha_s^3)$ correction decreases $\Gamma_t$ by $0.8\%$ of the previous $\mathcal{O}(\alpha_s^2)$ result, exceeding the error estimate by the usual scale-variation precription. Our to-date most precise theoretical prediction reads $\Gamma_t = 1.3148^{+0.003}_{-0.005} + 0.027\,(m_t - 172.69)\,$GeV, the error of which now meets the request by future colliders.
