Higgs-boson interactions within the Randall-Sundrum model

The scalar sector of the Randall-Sundrum model is discussed. The effective potential for the Standard Model Higgs-boson (h) interacting with Kaluza-Klein excitations of the graviton (h(mu)(nu n)) and the radion (phi) has been derived and it has been shown that only the Standard Model vacuum solution of partial derivativeV/partial derivativeh = 0 is allowed. The theoretical and experimental consequences of the curvature-scalax mixing xi R (H) over cap (dagger)(H) over cap introduced on the visible brane are considered and simple sum rules that relate the couplings of the mass eigenstates h and phi to pairs of vector bosons and fermions are derived. The sum rule for the ZZh and ZZphi couplings in combination with LEP/LEP2 data implies that not both the h and phi can be light. We present explicit results for the still allowed region in the (m(h), m(phi)) plane that remains after imposing the LEP upper limits for non-standard scalar couplings to a ZZ pair. The phenomenological consequences of the mixing axe investigated and, in particular, it is shown that the Higgs-boson decay h --> phiphi would provide an experimental signature for non-zero xi and can have a very substantial impact on the Higgs-boson searches, having BR(h --> phiphi) as large as 30 divided by 40 %.