On nuclear dependence of direct photon production

We have calculated the impact on theA dependence of direct photon production at large transverse momenta (p _T ) of models that were used successfully to explain the EMC effect. We find that, for energies andp _T 's typical of present direct photon measurements, the change in the photon yield due to nuclear modification of parton distributions can be expected to be about 15–20% on Fe. The effect is quite sensitive to the gluon distribution. In particular, for the models used in our calculations, theA dependence is affected more by the gluon distribution than by the quark distributions.