TOP-QUARK DECAYS INTO HEAVY-QUARK MESONS

For top quark decays into heavy quark mesons (B) over bar(c) and Y, a complete calculation to the leading order both in QCD coupling consta nt alpha(s) and in v, the typical velocity of the heavy quarks inside the mesons, is performed. Relations between the top quark mass and the decay branching ratios are studied. A comparison with the results whi ch are obtained by using the quark fragmentation functions is also dis cussed. The branching ratios are approximately consistent with that ob tained using fragmentation functions for large top quark masses, say, m(1)> 150 GeV, and are identical with them in the limit m(1)--> infini ty.