Search for Quarks in Cosmic Rays at Sea Level

A search for quarks has been conducted at sea level. No events have been found with energy losses by ionization in the range 0.06-0.165 and 0.25-0.65 that of singly charged minimum-ionizing particles. The experiment sets an upper limit on the fluxes as 6.6×${10}^{-11\mathrm{}}$ and 8.8×${10}^{-11\mathrm{}}$ ${\mathrm{cm}}^{-2\mathrm{}}$ ${\mathrm{sr}}^{-1\mathrm{}}$ ${\sec }^{-1\mathrm{}}$ for $\frac{1}{3}e$ and $\frac{2}{3}e$ minimum-ionizing quarks, respectively.