Blast from the past: Constraints on the dark sector from the BEBC WA66 beam dump experiment

TL;DR

This paper uses data from the 1982 CERN-WA-066 beam dump experiment to set new limits on millicharged dark particles and particles with dipole moments, improving previous bounds across a range of masses.

Contribution

It provides the first constraints on certain dark sector particles from the BEBC WA66 experiment, extending the mass bounds up to GeV scales.

Findings

Sets new limits on millicharged particles and dipole moments.

Improves bounds over previous experiments like CHARM II.

Extends constraints up to GeV mass range.

Abstract

We derive limits on millicharged dark states, as well as particles with electric or magnetic dipole moments, from the number of observed forward electron scattering events at the Big European Bubble Chamber in the 1982 CERN-WA-066 beam dump experiment. The dark states are produced by the 400 GeV proton beam primarily through the decays of mesons produced in the beam dump, and the lack of excess events places bounds extending up to GeV masses. These improve on bounds from all other experiments, in particular CHARM II.