Complete angular analysis of polarized top quark decay at O(αs) -: art. no. 054036

We calculate the full O(alpha(s)) radiative corrections to the three spin independent and five spin dependent structure functions that describe the angular decay distribution in the decay of a polarized top quark into a W boson (followed by the decay W+ --> l(+) v(l) or by W+ --> (q) over bar + q) and a bottom quark. The angular decay distribution is described in cascade fashion; i.e., the decay t(up arrow) --> W+ + X-b is analyzed in the top-quark rest system while the subsequent decay W+ --> l(+) + v(l) (or W+ --> (q) over bar + q) is analyzed in the V rest frame. Since the structure function ratios depend on the ratio in, lin, we advocate the use of such angular decay measurements for the determination of the top quark's mass. Our results for the eight O(alpha(s)) integrated structure functions are presented in analytical form, keeping the mass of the bottom quark finite. In the limit m(b) --> 0 the structure function expressions reduce to rather compact forms. We also present results for the m(b) = 0 unpolarized and polarized O(alpha(x)) scalar structure functions relevant to the semi-inclusive decay of a polarized top quark into a charged Higgs boson t(up arrow) --> H+ + X-b in the two-Higgs-doublet model when m(b) = 0.