Probing Millicharged Particles at an Electron Beam Dump with Ultralow-Threshold Sensors

TL;DR

This paper proposes using ultralow-threshold sensors, specifically Skipper-CCDs, in electron beam dumps to significantly improve the detection sensitivity for millicharged particles below 1.5 GeV, surpassing existing methods.

Contribution

It introduces a novel experimental setup with small ultralow-threshold silicon sensors to enhance the search for millicharged particles at accelerator facilities.

Findings

Sensitivity exceeds all existing searches for particles below 1.5 GeV.

A modest 2x14 Skipper-CCD array can achieve competitive or superior results.

Small-scale silicon devices can significantly extend experimental reach.

Abstract

We propose to search for millicharged particles produced in high-intensity electron beam dumps using small ultralow-threshold sensors. As a concrete example, we consider a Skipper-CCD placed behind the beam dump in Hall A at Jefferson Lab. We compute the millicharged particle flux, including both electromagnetic cascade and meson productions emanating from an aluminum target. We find that the sensitivity of a modest 2x14 array of Skipper-CCDs can exceed the sensitivity of all existing searches for millicharged particle masses below 1.5 GeV, and is either competitive or world leading when compared to other proposed experiments. Our results demonstrate that small-scale ultralow threshold silicon devices can enhance the reach of accelerator-based experiments, while fitting comfortably within existing experimental halls.