Greybody factors for black holes in four dimensions: Particles with spin

We compute the emission spectrum of minimally coupled particles with spin that are Hawking radiated from four-dimensional black holes in string theory. For a range of the black hole parameters the result has a product structure that may be interpreted in terms of the respective right- and left-moving thermal correlation functions of an effective string model. For spin-1 and spin-2 particles a novel cancellation between contributions to the wave function is needed to ensure this outcome. The form of the spectra suggests that the four-dimensional effective string description is ``heterotic:'' particles with spin are emitted from the right-moving sector, only.