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Cavendish Tests of Millicharged Particles

Asher Berlin1,2, Zachary Bogorad1,2, Peter W. Graham3,4, and Harikrishnan Ramani5

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Phys. Rev. Lett. 137, 021804 – Published 10 July, 2026

DOI: https://doi.org/10.1103/83fd-mnpk

Abstract

A terrestrial population of room-temperature millicharged particles can arise if they make up a dark matter subcomponent or if they are light enough to be produced in cosmic ray air showers. In a companion paper, we showed that a simple electrified shell acts as an efficient accumulator for such particles, parametrically enhancing their local density by many orders of magnitude. Here we demonstrate that Cavendish tests of Coulomb’s Law, performed since the late 18th century, function as both quasistatic accumulators and detectors for this overdensity. Reinterpretations of these past Cavendish tests thus provide some of the strongest bounds on a terrestrial millicharge population. We also propose surrounding a Cavendish test with an additional charged shell, which significantly improves the sensitivity and can even enable detection of the irreducible density of millicharged particles generated from cosmic rays. Using decades-old technology, this can outperform future accelerator searches for sub-GeV masses.

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Physics Subject Headings (PhySH)

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A Simple Search for Tiny Charges

Published 10 July, 2026

Decades-old experiments have now been enlisted to set new bounds on the properties of a hypothetical particle that bears a tiny fraction of the electron’s charge.

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See Also

Electric accumulation of millicharged particles

Asher Berlin, Zachary Bogorad, Peter W. Graham, and Harikrishnan Ramani
Phys. Rev. D 114, 015016 (2026)

Article Text

Supplemental Material

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Outline

Information

Phys. Rev. Lett. 137, 021804– Published 10 July, 2026
  • Received 17 November 2025
  • Revised 5 February 2026
  • Accepted 20 April 2026
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