Universal Extra Dimensions, Radiative Returns and the Inverse Problem at a Linear e+e- Collider

Understand

In a five-dimensional model with one Universal Extra Dimension (UED), signals for a pair of n = 1 Kaluza-Klein excitations could be easily observed at a future e+ e- collider if the process in question is kinematically allowed.

• However, these signals would prove difficult to distinguish from those predicted in other models, such as those with an extended gauge symmetry or supersymmetry.
• A much better power of discrimination is provided by the fact that the same machine could also produce the n=2 gauge bosons \gamma_2 and Z_2 as resonances in fermion pair-production without any upgrade in the collision energy \sqrt{s}.
• Assuming a fixed \sqrt{s}, as is expected at upcoming e+e- machines, we investigate the role of beam radiation in helping to excite such resonances through radiative returns.