Search for reactor-produced millicharged particles with Skipper-CCDs at the CONNIE and Atucha-II experiments

TL;DR

This paper reports the most stringent limits to date on the charge of millicharged particles, using Skipper-CCD sensors at the CONNIE and Atucha-II reactor experiments to detect low-energy interactions in the eV range.

Contribution

It provides the first combined analysis of data from two reactor experiments to set world-leading limits on millicharged particles across a broad mass range.

Findings

Established new upper limits on millicharged particle charge.

Demonstrated the effectiveness of Skipper-CCD sensors for low-energy particle detection.

Combined data enhances sensitivity over previous individual experiments.

Abstract

Millicharged particles, proposed by various extensions of the standard model, can be created in pairs by high-energy photons within nuclear reactors and can interact electromagnetically with electrons in matter. Recently, the existence of a plasmon peak in the interaction cross-section with silicon in the eV range was highlighted as a promising approach to enhance low-energy sensitivities. The CONNIE and Atucha-II reactor neutrino experiments utilize Skipper-CCD sensors, which enable the detection of interactions in the eV range. We present world-leading limits on the charge of millicharged particles within a mass range spanning six orders of magnitude, derived through a comprehensive analysis and the combination of data from both experiments.