143 Chapter 6: Heavy Quark Photon Production Radiation Fig. 6.3 demonstrates the effect of including all the terms generated by Eq. (6.4), not just the LO in 1 /E $^{+}$. Of course at higher E and p$_{T}$ the additional terms make little difference, but they regulate the otherwise divergent results in Δ p$_{T}$/p$_{T}$ as p$_{T}$ → 0. The Ter-Mikayelian effect, given by the difference between the m$_{γ}$ = 0 and m$_{γ}$ = 0 plots in Fig. 6.3, varies from 10-40% for charm and bottom energy loss. (a) (b) Figure 6.3: The effect of including all terms from Eq. (6.4) instead of just the leading order (LO) terms in 1 /E + for (a) Δ E/E and (b) Δ p$_{T}$/p$_{T}$ (the legend in (a) applies to both plots). For Δ E/E , the size of the relative difference in magnitude—the Ter-Mikayelian effect—is changed little while the overall normal- ization is significantly altered at low energies. For Δ p$_{T}$/p$_{T}$ both the relative and overall normalizations change quite a bit, with the inclusion of all terms regulating the p$_{T}$ → 0 divergences in the vacuum production radiation spectrum.