Graviton production by two photon and electron-photon processes in Kaluza-Klein theories with large extra dimensions - art. no. 116011

We consider the production of gravitons via two photon and electron-photon fusion in Kaluza-Klein theories which allow TeV scale gravitational interac tions. We show that at electron-positron colliders, the processes l(+)l(-) --> l(+)l(-)+ graviton, with l=e, mu, can lead to a new signal of low energ y gravity of the form l(+)l(-) + missing energy which is well above the sta ndard model background. For example, with two extra dimensions, at the Next Linear Collider with a center of mass energy of 500 or 1000 GeV, hundreds to thousands such l(+)l(-) + graviton events may be produced if the scale o f the gravitational interactions, M-D, is around a few TeV. At a gamma-elec tron collider, more stringent bounds may be placed on M-D via the related r eaction e(-)gamma-->e(-)G. For instance, if a 1 TeV e(+)e(-) collider is co nverted to an electron-photon collider, a bound of similar to 10(14) TeV ma y be placed on the scale M-D if the number of extra dimensions delta=2, whi le a bound of similar to 4(5) TeV may be placed if delta=4, with unpolarize d (right polarized) electron beams.