Review of Neutral Naturalness

TL;DR

Neutral naturalness offers symmetry-based solutions to the Higgs hierarchy problem, involving hidden sectors with unique gauge dynamics, dark matter candidates, and collider signals, requiring advanced nonperturbative studies.

Contribution

This review consolidates various models of neutral naturalness, explores their phenomenology, and highlights the importance of nonperturbative gauge dynamics and lattice studies for understanding hidden sectors.

Findings

Diverse realizations of neutral naturalness with collider signatures

Hidden sectors can produce dark matter candidates and connect to cosmology

Analysis of hidden-sector glueballs and quirks dynamics

Abstract

The hierarchy between the mass parameter of the Higgs boson and larger mass scales becomes ever more puzzling as experiments explore higher energies. Neutral naturalness is the umbrella term for symmetry-based explanations for these hierarchies whose quark symmetry partners are not charged under the SU(3) color gauge group of the Standard Model. Though the first manifestations of this idea predate the physics runs of the Large Hadron Collider, since the Higgs discovery this paradigm has grown and developed to include a wide variety of concrete realizations with connections to intriguing collider signals. Determining the phenomenology of such models often requires the characterization - typically relying on lattice calculations - of a new confining gauge symmetry. This presents additional motivation to further develop our understanding of nonperturbative field theory as well as to pursue specific lattice studies. The wide range of suggested hidden sectors also produces a variety of dark matter candidates, intersections with astrophysics and cosmology, and ties to neutrinos and flavor. In this review, we orient the reader within both this growing collection of specific models and the physical phenomena they produce. We also survey the often less familiar dynamics of hidden-sector glueballs and quirks. In addition to providing a guide to past efforts, we reveal interesting directions for further study.