Large bulk matter search for fractional charge particles

TL;DR

This study conducted the largest search to date for stable fractional charge particles in silicone oil using an advanced oil drop method, but found no evidence, setting a new upper limit on their abundance.

Contribution

It introduces an improved oil drop technique with electric field and air flow to enhance sensitivity in searching for fractional charge particles.

Findings

No fractional charge particles detected within the sensitivity limits.

Established a 95% confidence level upper limit of 1.15×10⁻²² particles per nucleon.

Set the most stringent constraints to date on fractional charge particle abundance in silicone oil.

Abstract

We have carried out the largest search for stable particles with fractional electric charge, based on an oil drop method that incorporates a horizontal electric field and upward air flow. No evidence for such particles was found, giving a 95% C.L. upper limit of $1.15\times 10^{-22}$ particles per nucleon on the abundance of fractional charge particles in silicone oil for $0.18 e \le |Q_{residual}| \le 0.82 e$.