Discerning noncommutative extra dimensions

Experimental limits on the violation of four-dimensional Lorentz invariance imply that noncommutativity among ordinary spacetime dimensions must be small. Noncommutativity among extra, compactified spatial dimensions, however, is far less constrained and may have discernible collider signatures. Here we study the experimental consequences of noncommutative QED in six dimensions, with noncommutativity restricted to a TeV-scale bulk. Assuming the orbifold T-2/Z(2), we construct the effective four-dimensional theory and study interactions unique to the noncommutative case. New vertices involving the Kaluza-Klein excitations of the photon yield order 100% corrections to the pair production and to the decays of some of the lighter modes. We show that these effects are difficult to resolve at the CERN LHC, but are likely within the reach of a future Very Large Hadron Collider.