Comparing Production Sources Spectrally

Neutrino number production rate versus energy in MeV for nucleon-nucleon bremsstrahlung (red, solid) and electron-positron annihilation (blue, dashed) for two temperature and density points in a representative post-collapse stellar profile. Note that bremsstrahlung always dominates neutrino/anti-neutrino pair production at low neutrino energies. In contrast, the emission spectrum for electron-positron annihilation is peaked at much higher energies at the temperatures and densities -- manifest here by domination above 70 and 10 MeV, respectively.