Electric Accumulation of Millicharged Particles

TL;DR

This paper proposes using an electrified shell to significantly accumulate millicharged particles near Earth, enhancing detection sensitivity and enabling new tests of Coulomb's law that surpass future accelerator experiments.

Contribution

It introduces a simple method to concentrate millicharged particles terrestrially, greatly improving detection prospects and enabling novel Coulomb's law tests with existing setups.

Findings

Electrified shells can boost millicharged particle density by up to twelve orders of magnitude.

Enhanced local density improves the sensitivity of detectors like ion traps.

Proposed method can explore parameter space beyond future accelerator capabilities.

Abstract

A terrestrial population of millicharged particles that interact significantly with normal matter can arise if they make up a dark matter subcomponent or if they are light enough to be produced in cosmic ray air showers. Such particles thermalize to terrestrial temperatures through repeated scatters with normal matter in Earth's environment. We show that a simple electrified shell (e.g., a Van de Graaff generator) functions as an efficient accumulator of such room-temperature millicharged particles, parametrically enhancing their local density by as much as twelve orders of magnitude. This can be used to boost the sensitivity of any detector housed in the shell's interior, such as ion traps and tests of Coulomb's law. In a companion paper, we apply this specifically to Cavendish tests of Coulomb's law, and show that a well-established setup can probe a large region of unexplored parameter space, with sensitivity to the irreducible density of millicharged particles generated from cosmic rays that outperforms future accelerator searches for sub-GeV masses.