Search for Light-Mass Fractionally Charged Particles in Space with DAMPE Experiment

Abstract: Free Fractionally Charged Particles (FCPs) are predicted by some theories beyond or extended to the standard model. FCPs have been widely searched for by underground and space-based experiments based on the assumption of heavy lepton-like particles. However, there is a paucity of research focusing on light-mass FCPs (LFCPs) in the sub-MeV mass range. In this work, we report the LFCPs in primary high energy cosmic rays, based on observational data from the Dark Matter Particle Explorer (DAMPE) satellite. This study utilized ten years on-orbit data of DAMPE to search for LFCPs with a charge of $\frac{2}{3}~e$. No LFCP candidate was observed. Upper flux limit of LFCPs with a mass of 0.511 MeV$/c<sup>{2}$ and a charge of $\frac{2}{3}~e$ is determined to be $$\rm 5.0 \times 10<sup>{-11}\,cm<sup>{-2}sr<sup>{-1}s<sup>{-1}$$ at the $\rm 90\%$ confidence level.