The LHC has recently started to collide proton beams and take its very first data.
It is designed to collide protons at 14 TeV, the highest center of mass (CM) energy ever reached in a laboratory - seven times higher than the current running Tevatron collider at Fermilab.
It is expected to significantly enlarge the kinematic region for the search for physics phenomena beyond the Standard Model (BSM). Several BSM theories predict the existence of other dimensions in addition
to the usual three spatial and one time dimension. Some of these models allow different particles to propagate into the extra-dimensional bulk.

We study the nature of Kaluza-Klein (KK) excitations in a specific extra-dimensional model where the SU(2)xU(1) gauge fields can exist in a single extra dimension (ED) compactified on a S^1/Z_2 orbifold, while the
matter fermions are localized in the usual 3d. We shall call this the S^1/Z_2 TeV^-1 ED model where we focus on the first excited KK mode of the SU(2)xU(1) gauge fields, photon and Z^0, denoted here
by photon*/Z*. We will search for a signal of the first KK excitation of the photon and Z^0
bosons.

In the LHC, these can be produced in the Drell-Yan process pp --> photon*/Z*--> l+ l- + X, where l is the final state charged lepton. The experimental signal which we search for in the ATLAS detector is therefore a heavy di-lepton final state, mu+ mu- + X or e+ e- + X, where the current experimental limits allow these productions at energies beyond 4
TeV.