Probing the Nature of Compactification with Kaluza-Klein Excitations at the Large Hadron Collider

It is shown that the nature of compactification of extra dimensions in theories of large radius compactification can be explored in several processes at the Large Hadron Collider (LHC). Specifically it is shown that the characteristics of the Kaluza-Klein (KK) excitations encode information on the nature of compactification, i.e., on the number of compactified dimensions as well as on the type of compactification, e.g., of the specific orbifold compactification. The most dramatic signals arise from the interference pattern involving the exchange of the Standard Model spin 1 bosons ($\gamma$ and Z) and their Kaluza-Klein modes in the dilepton final state $pp\to l^+l^-X$. It is shown that LHC with 100$fb^{-1}$ of luminosity can discover Kaluza-Klein modes up to compactification scales of $\approx 6$ TeV as well as identify the nature of compactification. Effects of the Kaluza-Klein excitations of the W boson and of the gluon are also studied. Exhibition of these phenomena is given for the case of one extra dimension and for the case of two extra dimensions with $Z_2\times Z_2, Z_3$, and $Z_6$ orbifold compactifications.