A Search for Lightly Ionizing Particles with the MACRO Detector

TL;DR

This paper reports a search for lightly ionizing particles with charges near that of an electron using the MACRO detector, finding no candidates and setting upper flux limits.

Contribution

It introduces a novel search method for lightly ionizing particles, including analysis of high multiplicity muon showers, with improved sensitivity.

Findings

No candidate particles observed in one year

Established upper flux limits for lightly ionizing particles

Extended search to high multiplicity muon events

Abstract

A search for lightly ionizing particles has been performed with the MACRO detector. This search was sensitive to particles with charges between $\fractional{5}$$e$ and close to the charge of an electron, with $\beta$ 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 $\Phi \leq 9.2 \times 10^{-15} cm^{-2} sec^{-1} sr^{-1}$ .