Dominance of virtual Delbrück scattering for the photon emission by nuclei in relativistic electron–nucleus and nucleus–nucleus collisions

We consider the contribution of virtual Delbrück scattering to the photon emission by nuclei in the collision of two ultra-relativistic nuclei Z1Z2→Z1Z2γ and electron–nucleus collisions eZ→eZγ, in the photon energy range m≪Eγ≪mγ, where m is the electron mass and γ is the Lorentz factor of the colliding nucleus. The discussed process has no infrared divergence. The total cross section is 50 barn for the Pb–Pb collisions at the LHC collider. The spectral distribution obtained is considerably larger than for ordinary nuclear bremsstrahlung in the same photon energy range.