Limits on the abundance of millicharged particles bound to matter

TL;DR

This paper presents a highly sensitive search for millicharged particles bound to matter, significantly improving the limits on their abundance and covering previously unexplored mass and charge ranges.

Contribution

It introduces a novel experimental approach that enhances sensitivity to millicharged particles with charges greater than 10^{-4}e, filling a gap in existing search efforts.

Findings

Sensitivity to millicharged particles improved by two orders of magnitude.

Explored a wide parameter space of mass and charge for stable bound states.

Set new upper limits on the abundance of such particles in matter.

Abstract

Millicharged particles (mCPs) are hypothesized particles possessing an electric charge that is a fraction of the charge of the electron. We report a search for mCPs with charges $\gtrsim 10^{-4}~e$ that improves sensitivity to their abundance in matter by roughly two orders of magnitude relative to previous searches. This search is sensitive to such particles over a wide range of masses and charges for which they can form stable bound states with matter, corresponding to a gap in parameter space that is beyond the reach of previous searches from accelerators, colliders, cosmic-ray experiments, and cosmological constraints.