2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/187088The basic box and phase space integrals needed to compute at second order the three-jet decay rate of the Z-boson into massive quarks are presented in this paper. Dimensional Regularization is used to regularize the infrared divergences that appear in intermediate steps. Finally, the cancellation of these divergences among the virtual and the real contributions is showed explicitly.14 pages, 2 figures, LaTeX, uses RevTeX, Some misprints corrected and new referencesHigh Energy Physics - Phenomenologytext