Search for lightly ionizing particles with the MACRO detector

A search for lightly ionizing particles has been performed with the MACRO detector. This search was sensitive to particles with charges between 1/5 e and close to the charge of an electron, with β between approximately 0.25 and 1.0. Unlike previous searches both single track events and tracks buried within high multiplicity muon showers were examined. In a period of approximately one year no candidates were observed. Assuming an isotropic flux, for the single track sample this corresponds to a 90% C.L. upper flux limit Φ ≤9.2×10-15 cm-2 s-1 sr-1. ©2000 The American Physical Society.