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Scientific Seminars

[Theory] Spin-2 KK Mode Scattering in the Truncated RS1

by Dennis Foren (Michigan State U)


The Randall-Sundrum model with two branes (RS1)  is a gravitational theory on five-dimensional spacetime. Because its fifth dimension is compactified, the theory manifests as a four-dimensional theory at low energies, where it describes interactions among a Kaluza-Klein spectrum that contains a 4D graviton, massless radion, and infinitely many massive spin-2 states. These massive spin-2 states pose a problem: most tree-level diagrams describing their 2-to-2 scattering at center-of-momentum energy E grow as fast as O(E^10) despite the 5D theory forbidding growth faster than O(E^2).

This talk will discuss how cancellations between infinitely many diagrams in the 4D theory restore the O(s) growth required by the 5D theory. In particular, these cancellations are demonstrated numerically (and discussed analytically) for the case of helicity-zero elastic scattering. This talk will also demonstrate how truncating the spin-2 KK tower in RS1 to only a couple of states or choosing to neglect the radion can lead to erroneously large matrix elements, even at experimentally interesting energy scales.