photon-photon collisions via heavy ion beams at LHC

The cross sections for the production of hadrons in quasi real photonphoton collisions in heavy ion interactions are compared with the corresponding cross sections for central diffraction. The signatures, heavy ions with only slightly changed momenta together with two large rapidity gaps and a cluster of produced hadrons in the central region, are nearly identical in both processes. Therefore, it will be rather difficult to distinguish the two reactions experimentally. It is found, that central diffraction is the dominant process in collisions of protons, light and medium-heavy ions. The photon-photon process dominates in collisions of heavy ions like lead. Preprint US–FT / 18–96 Preprint SI 96-04 † Visiting professor IBERDROLA. Permanent address: Department of High Energy Physics, University of St. Petersburg, 198904 Russia