Search for Millicharged Particles Using Optically Levitated Microspheres

TL;DR

This study used optically levitated microspheres in high vacuum to search for stable millicharged particles in bulk matter, setting new upper limits on their abundance and demonstrating a novel sensitive force measurement technique.

Contribution

It presents the first direct search for single millicharged particles bound in macroscopic matter using optically levitated microspheres.

Findings

No evidence of millicharged particles was found.

Set an upper limit on particle abundance of 2.5 x 10^{-14} per nucleon.

Demonstrated sensitive force measurement capability with levitated microspheres.

Abstract

We report results from a search for stable particles with charge > $10^{-5}$ e in bulk matter using levitated dielectric microspheres in high vacuum. No evidence for such particles was found in a total sample of 1.4 ng, providing an upper limit on the abundance per nucleon of 2.5 x $10^{-14}$ at the 95% confidence level for the material tested. These results provide the first direct search for single particles with charge < 0.1 e bound in macroscopic quantities of matter and demonstrate the ability to perform sensitive force measurements using optically levitated microspheres in vacuum.