Signals for noncommutative QED ineγandγγcollisions

We study the effects of noncommutative QED (NCQED) in fermion pair production, $\gamma +\gamma \to f+\overline{f},$ and Compton scattering, $e+\gamma \to e+\gamma .$ Non-commutative geometries appear naturally in the context of string or M theory and give rise to 3- and 4-point photon vertices and to momentum dependent phase factors in QED vertices which will have observable effects in high energy collisions. We consider $e^{+}{e}^{-}$ colliders with energies appropriate to the TeV linear collider proposals and the multi-TeV CLIC project operating in $\gamma \gamma$ and $e\gamma$ modes. Noncommutative scales roughly equal to the center of mass energy of the $e^{+}{e}^{-}$ collider can be probed, with the exact value depending on the model parameters and experimental factors. However, we find that the Compton process is sensitive to ${\Lambda }_{\mathrm{NC}}$ values roughly twice as large as those accessible to the pair production process.