Speaker
Description
In this talk we will discuss the recent processes in the calculation of the high-order perturbative corrections to the semi-inclusive production and decay of top quarks at lepton colliders at N3LO in QCD. In particular, the talk will be focusing on the first high-precision calculation of the complete QCD corrections to the top-quark decay width $\Gamma_t$, $W$-helicity fractions and semi-inclusive distributions to the third order in the strong coupling constant $\alpha_s$. 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 considerably the error estimated by the usual scale-variation prescription. With this critical piece of correction included, we arrive at the to-date most precise theoretical prediction which meets the envisaged precision request by future hadron and lepton colliders.
