Search for Fractionally Charged Particles

We have performed a geophysical search for fractionally charged particles in seawater and rock samples. The samples were run through cation exchange columns to separate most of the material from particles of charge $\pm \frac{2}{3}$ and $\pm \frac{1}{3}$. The purified samples were converted into azides and evaporated in an electron gun, which accelerated the negatively charged particles to a solid-state detector. Quarks with charge $+\frac{2}{3} \left(q_1\right)$ would probably evaporate from azides as ($q_1+e$) and would thus have an effective charge of $-\frac{1}{3}$. The pulse-height spectra from the detector were scanned for peaks corresponding to particles of a charge between -1 and 0; no such particles were found. Limits on the concentration of $q_1$ quarks are ≲${10}^{-23\mathrm{}}$ quarks/nucleon in the rock samples and ≲${10}^{-24\mathrm{}}$ quarks/nucleon in the seawater samples. These limits depend, of course, on the assumptions concerning the chemical behavior of quarks made in the text.