Higgs-induced screening mechanisms in scalar-tensor theories.

Abstract

We consider the theory of a light conformally coupled scalar field, that is, one that is coupled directly to the Ricci scalar of the gravitational sector. This theory can be written equivalently as one of a light scalar that is coupled to the Standard Model of particle physics with a particular combination of Higgs-portal couplings. When the conformal coupling function contains terms that are linear and quadratic in the conformally coupled scalar, we find that the effective mass of the light propagating mode and its coupling to matter fields, obtained after expanding around a minimum of the classical potential, depend on the energy density of the background environment. This is despite the absence of nonlinear terms in the original equationof motion for the light conformally coupled field. Instead, we find that the nonlinearities of the prototype Higgs potential are communicated to the light mode. In this way, we present a novel realization of screening mechanisms, in which light degrees of freedom coupled to the Standard Model are able to avoid experimental constraints through environmental and thin-shelleffects.