LEGEND-200's Sensitivity to Fractionally Charged Particles

LEGEND-200 is an ultra-low-background experiment designed to search for neutrinoless double-beta decay using high-purity germanium detectors enriched in ⁷⁶Ge. Its low background and high sensitivity also enable searches for Beyond-the-Standard-Model physics. This work presents simulation studies of fractionally charged particles (FCPs) passing through LEGEND-200 to assess the experiment’s sensitivity to such particles. FCPs are hypothetical particles carrying an electric charge smaller than the elementary charge e. This study evaluates whether LEGEND-200 can set a world-leading limit on the FCP flux and explores how a new data-taking strategy could improve sensitivity. Based on simulation results, LEGEND-200 can set a world-leading limit in the charge range e/70 to e/18 with one year of data, extended to e/14 with three years. This represents up to a 29× (83×) improvement over the current best limit for one (three) years of data.