Fractionally Charged Particles at the Energy Frontier: The SM Gauge Group and One-Form Global Symmetry

TL;DR

Discovering fractionally charged particles at the LHC could reveal new nonperturbative aspects of the Standard Model and challenge existing unification theories, with some searches yet to be fully explored.

Contribution

This paper analyzes the phenomenology, current constraints, and theoretical implications of fractionally charged particles, emphasizing their potential for discovery and the importance of global symmetry frameworks.

Findings

Current collider bounds are often surprisingly weak or absent.

Fractionally charged particles have distinctive signatures that enhance discovery prospects.

Theoretical frameworks highlight the significance of global symmetries in understanding these particles.

Abstract

The observed Standard Model is consistent with the existence of vector-like species with electric charge a multiple of $e/6$. The discovery of a fractionally charged particle would provide nonperturbative information about Standard Model physics, and furthermore rule out some or all of the minimal theories of unification. We discuss the phenomenology of such particles and focus particularly on current LHC constraints, for which we reinterpret various searches to bound a variety of fractionally charged representations. We emphasize that in some circumstances the collider bounds are surprisingly low or nonexistent, which highlights the discovery potential for these species which have distinctive signatures and important implications. We additionally offer pedagogical discussions of the representation theory of gauge groups with different global structures, and separately of the modern framework of Generalized Global Symmetries, either of which serves to underscore the bottom-up importance of these searches.