Gluon radiation in tt̄ production at the Fermilab Tevatron pp̄ collider

We present a complete calculation of the matrix elements for the processes qq̄,gg→bW+b̄W-g and qg→bW+b̄W-q which are relevant for the study of events with an additional jet in tt̄ production at the Fermilab Tevatron pp̄ collider. Our calculation includes (i) the contributions from gluons emitted during the top quark production and decay stages and the interference between these, and (ii) the complete set of Feynman diagrams corresponding to both resonant and nonresonant top quark production. We study the distribution in phase space of the additional parton jet and make comparisons with previous studies based on the soft-gluon approximation and with results from parton-shower Monte Carlo simulations. The implications for top quark mass measurements are briefly discussed.