QCD radiation off heavy particles

We study QCD radiation in decay processes involving heavy particles. As inp ut, the first-order gluon emission rate is calculated in a number of reacti ons, and comparisons of the energy flow patterns show a non-negligible proc ess dependence. To proceed further, the QCD parton shower language offers a convenient approach to include multi-gluon emission effects, and to descri be exclusive event properties. An existing shower algorithm is extended to take into account the process-dependent mass, spin and parity effects, as g iven by the matrix element calculations. This allows an improved descriptio n of multiple gluon emission effects off b and t quarks, and also off nonst andard particles like squarks and gluinos. Phenomenological applications ar e presented for bottom production at LEP, Higgs particle decay to heavy fla vours, top production and decay at linear colliders, and some simple supers ymmetric processes. (C) 2001 Published by Elsevier Science B.V.