Speaker
国富 徐
(山东大学物理学院)
Description
We present the next-to-next-to-leading-order (NNLO) QCD corrections to the
angular distribution of the polarized top-quark decay
$t(\uparrow)\to W^+X_b$, followed by $W^+\to\ell^+\nu_\ell$, with an on-shell
$W$ boson. We compute eight helicity structure functions, comprising
three spin-independent and five spin-dependent functions, through
$\mathcal{O}(\alpha_s^2)$, both in the massless-bottom approximation and with
the bottom-quark mass retained. These results extend the complete
next-to-leading-order angular analysis to NNLO and provide consistent
predictions for the total decay width, the $W$-boson helicity fractions,
polar-angle asymmetries, azimuthal correlations, and the elements of the
top--$W$ double density matrix.
