  A possible setup for the experimental verification of linear Breit-Wheeler
pair creation of electrons and positrons in photon-photon collisions is studied
theoretically. It combines highly energetic bremsstrahlung photons, which are
assumed to be generated by an incident beam of GeV electrons penetrating
through a high-$Z$ target, with keV photons from an X-ray laser field, which is
described as a focused Gaussian pulse. We discuss the dependencies of the pair
yields on the incident electron energy, target thickness, laser parameters, and
collision geometry. It is shown that, for suitable conditions which are
nowadays in reach at X-ray laser facilities, the resulting number of created
particles seems to be well accessible for enabling the first experimental
observation of the linear Breit-Wheeler process $\gamma\gamma\to e^+e^-$.

High Energy Physics - Phenomenology