0th Order Heavy Quark Photon Bremsstrahlung
  We calculate the 0th order in opacity number distribution of massive photons (gluons) for heavy quark production radiation including interference from the away-side jet. While consistent with the soft photon (gluon) approximation, we find that approximating 1-x with 1, as done in previous calculations, strongly affects the magnitude of energy loss. Restoring gauge invariance by including the radiation associated with the away-side jet fills in the "dead cone," but is a relatively small effect. The Ter-Mikayelian reduction from vacuum energy loss is 10-40% for 5-25 GeV charm and bottom quarks. 
W. A. Horowitz