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Microdrop Technology And The Search for Fractional Charge Particles
PARC Forum

30 May 2002
George E. Pake Auditorium

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All known elementary particles that can be isolated – electrons, protons, neutrons, photons, muons – have an electric charge nq where q is the magnitude of the electron's charge and n is 0 or an integer. Are there elementary particles with fractional electric charge, such as q/5 or pi-q, that can be isolated? (Quarks are assumed to have q/3 or 2q/3 charge but so far have never been found in isolation.) We have been searching in bulk matter for elementary particles with fractional electric charge using advanced forms of the Millikan oil drop experiment. So far we have negative results.

Our search philosophy assumes that the sought particles would have been produced in the early universe. The experimental methods will be described with emphasis on the microdrop technologies we have developed to use non-aqueous liquids and liquids containing suspended, natural minerals such as meteoritic material from asteroids.


Martin Perl was awarded the 1995 Nobel Prize in Physics. In the mid-1970s, working on the Stanford Positron-Electron Asymmetric Ring (SPEAR) with a collaboration of 30 other physicsts from SLAC and Lawrence Berkeley National Laboratory, Perl began to find event records by their detector that could not be explained by any of the known subatomic particles. After more than a year of analysis, Perl was able to convince the rest of his team that they were in fact observing a new and different type of elementary particle, which he named the tau. In the Standard Model of particle physics, the elementary building blocks of matter appear in families, with two leptons and two quarks in each. Until Perl's discovery there were only two such families known to exist.

Dr. Perl discovered the first member of a third quark-lepton family. In 1976, the bottom quark was discovered by Fermi National Accelerator Laboratory, followed in 1995 by the discovery of the third member: the top quark. Perl was awarded the Wolf Prize for his discovery of the tau in 1982. Dr. Perl received his Ph.D. in 1955 from Columbia University, where he studied under Professor I. I. Rabi, winner of the 1944 Nobel Prize in physics. He is a member of the National Academy of Sciences and a Fellow of the American Physical Society (APS).


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