Gluon Radiation and Energy Losses in Top Quark Production
  The emission of energetic gluons in $\tt$ production in $\ee$ annihilation can have important experimental consequences, in particular on top quark mass measurements. We present compact, analytical expressions for the gluon energy distribution and its average value at first order in QCD perturbation theory. Our results are valid for arbitrary masses, collision energies and production currents. We pay particular attention to top quark production near threshold, and show that in certain cases the soft gluon approximation is insufficient to describe the radiation spectrum. 
Yu.L. Dokshitzer, V.A. Khoze and W.J. Stirling