High energy photon colliders (γγ,γe) are based on e-e-linear colliders where high energy photons are produced using Compton scattering of laser light on high energy electrons just before the interaction point. This paper is a part of the Technical Design Report of the linear collider TESLA.1Physics program, possible parameters and some technical aspects of the photon collider at TESLA are discussed.

The lepton number violating signal of like-sign-dileptons (LSD), pp → ℓ ± ℓ ± + 2jets, is investigated within a model of mixing in the neutrino sector assuming 12.60. 13.15.+g, 14.60.St, Typeset using REVT E X