Search for particles with charge 2/3e in cosmic rays

Abstract
The flux of particles with charge equal to [Formula: see text] of the electron charge which reach sea level from the vertical with relativistic velocities was found to be less than 2.7 × 10−10 cm−2 sr−1 s−1 at 90% confidence level. The particles were identified through their characteristic energy loss in a 48-counter hodoscope. The result seems inconsistent with a model of hadrons as being a composite of quarks.