Improved search for elementary particles with fractional electric charge

Nancy M. Mar, Eric R. Lee, George R. Fleming, Brendan C.K. Casey, Martin L. Perl, Edward L. Garwin, Charles D. Hendricks, Klaus S. Lackner, Gordon L. Shaw

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


We have devised and demonstrated the successful operation of a low-cost, high-mass throughput technique capable of performing bulk matter searches for fractionally charged particles based on an improved Millikan liquid drop method. The method uses a stroboscopic lamp and a charge coupled device video camera to image the trajectories of silicone oil drops falling through air in the presence of a vertical, alternating electric field. The images of the trajectories are computer processed in real time, the electric charge on a drop being measured with an rms error of 0.025 of an electron charge. This error is dominated by Brownian motion. In the first use of this method, we have looked at 5 974 941 drops and found no evidence for fractional charges in 1.07 mg of oil. With 95% confidence, the concentration of isolated quarks with ±1/3e or ±2/3e in silicone oil is less than one per 2.14×1020 nucleons.

Original languageEnglish (US)
Pages (from-to)6017-6032
Number of pages16
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Issue number11
StatePublished - 1996
Externally publishedYes

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Physics and Astronomy (miscellaneous)


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