Search for Magnetic Monopole Pair Production in Ultraperipheral (Formula Presented) Collisions at (Formula Presented) With the Atlas Detector at the Lhc

Abstract

This Letter presents a search for highly ionizing magnetic monopoles in (Formula presented) of ultraperipheral (Formula presented) collision data at (Formula presented) collected by the ATLAS detector at the LHC. A new methodology that exploits the properties of clusters of hits reconstructed in the innermost silicon detector layers is introduced to study highly ionizing particles in heavy-ion data. No significant excess above the background, which is estimated using a data-driven technique, is observed. Using a nonperturbative semiclassical model, upper limits at 95% confidence level are set on the cross section for pair production of monopoles with a single Dirac magnetic charge in the mass range of 20-150 GeV. Depending on the model, monopoles with a single Dirac magnetic charge and mass below 80-120 GeV are excluded. © 2025 CERN, for the ATLAS Collaboration.