Non-Decoupling New Particles

TL;DR

This paper introduces 'Loryons', a new class of non-decoupling particles whose masses are Higgs vacuum expectation value-dependent, with implications for electroweak symmetry realization and current experimental constraints.

Contribution

It defines Loryons, classifies their representations, and analyzes experimental bounds, highlighting the open scalar parameter space for future discovery.

Findings

Most fermionic Loryons are ruled out by current data.

Scalar Loryons still have large unexplored parameter space.

Discovery of Loryons would imply non-linear electroweak symmetry realization.

Abstract

We initiate the study of a new class of beyond the Standard Model states that we call "Loryons." They have the defining characteristic of being non-decoupling, in the sense that their physical mass is dominated by a contribution from the vacuum expectation value of the Higgs boson. The stakes are high: the discovery of a Loryon would tell us that electroweak symmetry must be non-linearly realized in the effective field theory of the Standard Model. Loryons have their masses bounded from above by perturbative unitarity considerations and thus define a finite parameter space for exploration. After providing a complete catalog of Loryon representations under mild assumptions, we turn to examining the constraints on the parameter space from Higgs couplings measurements, precision electroweak tests, and direct collider searches. We show that most fermionic candidates are already ruled out (with some notable exceptions), while much of the scalar Loryon parameter space is still wide open for discovery.