Photon-Photon Physics with Heavy Ions at CMS

Relativistic heavy ion beams are an intense source of ( quasireal) photons with a spectrum extending up to several hundred GeV, due to the high charge Z and the large energy of the ions. In this note we discuss the possibility of using this in peripheral collisions for photon-photon physics. We discuss the total luminosities that can be achieved with different ion species. In order to suppress central collisions an efficient trigger for peripheral collisions is needed, that is, for the two ions to remain intact during the collision. We discuss the physical potential of these collisions especially for the search for new physics up to gamma gamma invariant masses of about 100~GeVand the hadron spectroscopy. Some aspect of this were discussed in detail in connection with the Letter of Intent for FELIX ( CERN/LHCC 97-45, LHCC/I10) and we refer the reader to it for more details.