Subthreshold photons in heavy-ion reactions at intermediate energies

In the present talk, I discuss about the properties of the energetic photons produced in heavy-ion reactions. I show that they are sensitive to the maximum density reached in the first stage of the nuclear reaction. Then, the existence of a thermal contribution to the photon differential cross-section is discussed. These photons are sensitive to the properties of the Equation-of-State, to the dynamics of the reaction and represent a new thermometer of heated nuclear matter. I finally describe the future experiments plainfield at KVI and GANIL. (author)