Large Bulk Matter Search for Fractional Charge Particles
United States. Department of Energy. Office of Energy Research, 2002 - 5 pages
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% confidence level upper limit of 1.17 x 10−22 particles per nucleon on the abundance of fractional charge particles in silicone oil for 0.18e d."