Search for Fractional-Charge Particles in Meteoritic Material

We have used an automated Millikan oil drop method to search for free fractional-charge particles in a sample containing in total 3.9 mg of pulverized Allende meteorite suspended in 259 mg of mineral oil. The average diameter of the drops was $26.5\mu \mathrm{m}$ with the charge on about 42 500 000 drops being measured. This search was motivated by the speculation that isolatable, fractional-charge particles produced in the early Universe and present in our Solar System are more likely to be accumulated in asteroids than on Earth‘s surface. No evidence for fractional-charge particles was found. With 95% confidence, the concentration of particles with fractional-charge more than 0.25 $e$ ($e$ being the magnitude of the electron charge) from the nearest integer charge is less than $1.3\times {10}^{-21}$ particles per nucleon in the meteoritic material and less than $1.9\times {10}^{-23}$ particles per nucleon in the mineral oil.

Figure 1

Search apparatus.

Figure 2

The $q$ charge distribution in units of $e$.

Figure 3

The $q_c$ charge distribution in units of $e$.

Figure 4

The $q_c$ residual charge distribution in units of $e$.