ON GLUON RADIATION IN T(T)OVER-BAR PRODUCTION AND DECAY

Understanding the pattern of gluon radiation in t (t) over bar product ion processes is important for making an accurate determination of the top mass from the measurement of its decay products. In a recent pape r we showed that the exact matrix element and parton shower (HERWIG) c alculations gave very different results for the distribution of gluon jets in t (t) over bar production at the Tevatron p (p) over bar colli der. By repeating the calculation for the simpler e(+)e(-) --> b (b) o ver bar W(+)W(-)g process, we reveal even more dramatic differences be tween the two approaches. We conclude that there are significant diffe rences in gluon radiation between HERWIG and the matrix element calcul ation in regions of phase space where one would expect agreement.