Signals for Non-Commutative QED in $e γ$ and $γγ$ Collisions

Abstract

We study the effects of non-commutative QED (NCQED) in fermion pair production, $γ+ γ\to f + \bar{f}$ and Compton scattering, $e + γ\to e + γ$. Non-commutative geometries appear naturally in the context of string/M-theory and gives 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 $γγ$ and $eγ$ modes. Non-commutative 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 found that the Compton process is sensitive to $Λ_{NC}$ values roughly twice as large as those accessible to the pair production process.