Radion dynamics and electroweak physics

Abstract

The dynamics of a stabilized radion in the Randall-Sundrum model with two branes is investigated, and the effects of the radion on electroweak precision observables are evaluated. The radius is assumed to be stabilized using a bulk scalar field as suggested by Goldberger and Wise. First the mass and the wave function of the radion is determined including the back reaction of the bulk stabilization field on the metric, giving a typical radion mass of the order of the weak scale. This is demonstrated by a perturbative computation of the radion wave function. A consequence of the background configuration for the scalar field is that after including the back reaction the Kaluza-Klein states of the bulk scalars couple directly to the standard model fields on the TeV brane. Some cosmological implications are discussed, and in particular it is found that the shift in the radion at late times is in agreement with the four-dimensional effective theory result. The effect of the radion on the oblique parameters is evaluated using an effective theory approach. In the absence of a curvature-scalar Higgs mixing operator, these corrections are small and give a negative contribution to S. In the presence of such a mixing operator, however, the corrections can be sizable due to the modified Higgs and radion couplings.

Light signals from a lighter Higgs

“…A simple example is that of a singlet scalar, φ, which has been extensively discussed (see e.g., [5][6][7][8][9][10][11][12]). To allow for production from gluon fusion at the LHC the singlet must couple to extra vectorlike colored matter, yφΨΨ, necessitating the introduction of many new degrees of freedom.…”

Randall–Sundrum reality at the LHC

“…Goldberger and Wise showed that a bulk scalar field propagating in the background geometry, Eq. (1), can generate a potential that can stabilize L. [24] In order to reproduce the value kL ≃ 35, the radion should have a lighter mass than that of the Kaluza-Klein modes of all bulk fields [25]. Thus, the detection of the radion may well be expected as the first signal to indicate that the RS model is truly realized in nature.…”

Effective theory of a light dilaton

“…Radion stabilization using the GoldbergerWise mechanism [43] can be understood as a stable minimum for the dilaton potential being generated by effects which explicitly violate conformal symmetry [27]. Several authors have studied the couplings of the radion in Randall-Sundrum models, both in the case when the SM fields are localized to a brane [43][44][45][46] and in the case when they are in the bulk [47,48]. We find excellent * A closely related result has been obtained in the context of walking gauge theories using current algebraic methods [31].…”