Magnetic monopoles as probes of the global structure of the Standard Model

TL;DR

This work links the global structure of the Standard Model gauge group to monopole phenomenology by showing that the UV monopole spectrum, as classified by $G_{SM}/Z_p$, projects to only two infrared monopoles with magnetic charges $3 g_D$ and $6 g_D$ after EWSB. The authors use a magnetic 1-form symmetry framework to justify the IR selection rule and quantify relic abundances for different UV embeddings, demonstrating natural suppression at low symmetry-breaking scales. They further study monopole interactions with matter via the KYG-modified Bethe–Bloch formula and perform CORSIKA+CONEX Monte Carlo simulations to confirm that the energy loss per unit length scales as $g^2$ for Lorentz factors $\gamma \lesssim 10^4$ and that $M'_3$ and $M'_6$ can produce clean observational signatures. This work provides a concrete, testable link between SM global structure and cosmic-ray monopole signatures, guiding future searches for highly ionising tracks to constrain UV completions.

Abstract

The magnetic charges of monopoles arising in ultraviolet completions of the Standard Model are constrained by the global structure of the gauge group. After electroweak symmetry breaking, a subset of the ultraviolet monopoles carrying magnetic charges 3$g_D$ and $6g_D$ can survive as isolated, colour-neutral states in the infrared. We show that this selection rule follows from the interplay between the symmetry structure and the magnetic 1-form symmetry, and discuss how the relic abundance of such monopoles can be naturally suppressed by the symmetry breaking scale. We further demonstrate that such monopoles with Lorentz factor $γ\lesssim 10^4$ propagate through matter with ionisation energy loss profiles scaling as $g^2$ using CORSIKA Monte Carlo simulations.

Figures (2)

• Figure 1: Average energy loss by ionisation per unit atmospheric depth for magnetic monopoles with charges $g = n g_D$ propagating through the atmosphere, shown as a function of column depth. The upper and lower panels correspond to Lorentz factors $\gamma = 10^{3}$ and $\gamma = 10^{4}$, respectively. The curves correspond to $n = 1, 2, 3, 6$. The depth range shown focuses on the region where the monopole has fully entered the atmosphere, and the stopping power varies slowly with depth.
• Figure 2: Ratio of the average energy loss by ionisation per unit atmospheric depth for magnetic monopoles with charge $g = n g_D$ relative to the unit Dirac charge case, shown as a function of depth. The upper and lower panels correspond to $\gamma = 10^{3}$ and $\gamma = 10^{4}$, respectively. The ratios are approximately constant and follow the expected $n^2$ (equivalently $g^2$) scaling within the ionisation-dominated velocity regime.