Graviton Production By Two Photon and Electron-Photon Processes In Kaluza-Klein Theories With Large Extra Dimensions

We consider the production of gravitons via two photon and electron-photon fusion in Kaluza-Klein theories which allow TeV scale gravitational interactions. 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 energy gravity of the form l+l- -> l+l- + missing energy which is well above the Standard 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 of the gravitational interactions, M_D, is around a few TeV. At a gamma-electron collider, more stringent bounds may be placed on M_D via the related reaction e^-\gamma -> e^- graviton. For instance, if a 1TeV electron positron collider is converted to an electron-photon collider, a bound of ~10TeV may be placed on the scale M_D if the number of extra dimensions delta=2 while a bound of ~4TeV may be placed if delta=4.