Kaluza-Klein states from large extra dimensions

Abstract

We consider the novel Kaluza-Klein (KK) scenario where gravity propagates in the $(4+n)$-dimensional bulk of spacetime, while gauge and matter fields are confined to the $(3+1)$-dimensional world volume of a brane configuration. For simplicity we assume compactification of the extra n dimensions on a torus with a common scale $R,$ and identify the massive KK states in the four-dimensional spacetime. For a given KK level $\stackrel{\ensuremath{\rightarrow}}{n}$ there is one spin-2 state, $(n\ensuremath{-}1)$ spin-1 states, and $n(n\ensuremath{-}1)/2$ spin-0 states, all mass degenerate. We construct the effective interactions between these KK states and ordinary matter fields (fermions, gauge bosons, and scalars). We find that the spin-1 states decouple and that the spin-0 states only couple through the dilaton mode. We then derive the interacting Lagrangian for the KK states and standard model fields, and present the complete Feynman rules. We discuss some low-energy phenomenology for these new interactions for the case when $1/R$ is small compared to the electroweak scale, and the ultraviolet cutoff of the effective KK theory is on the order of 1 TeV.