Higgs-Boson Mass Limit within the Randall-Sundrum Model

Abstract

Perturbative unitarity for $\wlwl$ scattering is discussed within the Randall-Sundrum model. It is shown that the exchange of massive 4D Kaluza-Klein gravitons leads to amplitudes growing linearly with the CM energy squared. Summing over KK gravitons up to a scale $\lbar$ and testing unitarity at $\rts=\lbar$, one finds that unitarity is violated for $\lbar$ below the 'naive dimensional analysis' scale, $\lnda$. It is also shown that the exchange of gravitons can substantially relax the upper limit from unitarity on the mass of the Standard Model Higgs boson - consistency with unitarity for all $\rts$ below $\lbar$ is possible for $\mh$ as large as $ 1.4\tev$, depending on the curvature of the background metric. Observation of the mass and width (or cross section) of one or more KK gravitons at the LHC will directly determine the curvature and the scale $\lw$ specifying the couplings of matter to the KK gravitons. With this information and a measurement of the Higgs boson mass it will be possible to determine the precise $\rts$ value below which unitarity will remain valid.