Limits on millicharged matter from beam-dump experiments.

Abstract

It has been proposed by Goldberg and Hall that the dark matter in galactic halos may be a type of shadow matter which interacts electromagnetically with ordinary matter (via a mixing effect) with effective charge \ensuremath{\Vert}Q\ensuremath{\Vert}=2\ensuremath{\epsilon}e where \ensuremath{\epsilon}\ensuremath{\ll}1. We put constraints on the mass (${m}_{s}$) and effective charge (i.e., \ensuremath{\epsilon}) of such particles by examining their possible production and detection in high-statistics proton beam-dump experiments. We find, for example, that \ensuremath{\epsilon}\ensuremath{\lesssim}2\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}2}$ for 1\ensuremath{\lesssim}${m}_{s}$\ensuremath{\lesssim}200 MeV.