Renormalizable Models of Flavor-Specific Scalars

Abstract

New light singlet scalars with flavor-specific couplings represent a phenomenologically distinctive and flavor-safe alternative to the well-studied possibility of Higgs-portal scalars. However, in contrast to the Higgs portal, flavor-specific couplings require an ultraviolet completion involving new heavy states charged under the Standard Model gauge symmetries, leading to a host of additional novel phenomena. Focusing for concreteness on a scenario with up quark-specifc couplings, we investigate two simple renormalizable completions, one with an additional vector-like quark and another featuring an extra scalar doublet. We consider the implications of naturalness, flavorand CP-violation, electroweak precision observables, and direct searches for the new states at the LHC. These bounds, while being model-dependent, are shown to probe interesting regions in the parameter space of the scalar mass and its low-energy effective coupling, complementing the essential phenomenology of the low-energy effective theory at a variety of low and medium energy experiments.

The Forward Physics Facility: Sites, Experiments, and Physics Potential

“…The dot-dashed line illustrates the mass and mixing angle for an inflaton that decays when the universe reaches a density around the electroweak scale of ρ ∼ (100 GeV) 4 , corresponding to a lower coupling limit motivated by the incorporation of electroweak baryogenesis. In addition, scalars with couplings different from the Higgs mixing expectation have been considered at forward LHC detectors in the case of dominant couplings to muons [77] or up quarks [31,78], an additional coupling to the Higgs boson [79], as well as the dilaton of Ref. [80] employed to address the hierarchy problem.…”

Hadrophilic Dark Sectors at the Forward Physics Facility

“…Finally, although we do not consider them in this work, viable models of hadrophilic scalar mediators can also be constructed; see, e.g., Refs. [34][35][36]. However, for the incident DM energies in the TeV range relevant for FPF experiments, scalar-mediated DM-nuclear scattering rates are typically suppressed by several orders of magnitude in comparison to vector-mediated scattering rates; see also Ref.…”

Probing Invisible Vector Meson Decays with NA64 and LDMX

“…In the minimal case of a Higgs-mixed scalar, the mediator couples to quarks proportionally to their mass, and thus our signatures are not competitive with collider and B meson constraints [98], which already exclude most of the thermal relic target. On the other hand, it may be possible to probe new parameter space in models where the scalar preferentially couples to light quarks [99][100][101].…”