Soft-gluon resummation for bottom fragmentation in top quark decay

We study soft-gluon radiation in top quark decay within the framework of perturbative fragmentation functions. We present results for the b-quark energy distribution, accounting for soft-gluon resummation to next-to-leading logarithmic accuracy in both the MS-bar coefficient function and in the initial condition of the perturbative fragmentation function. The results show a remarkable improvement and the b-quark energy spectrum in top quark decay exhibits very little dependence on factorization and renormalization scales. We present some hadron-level results in both xB and moment space by including non-perturbative information determined from e+e- data. (author)