The Ricochet experiment

Coherent elastic neutrino-nucleus scattering (CEvNS) is a long-predicted interaction that was only recently observed experimentally. As a neutral current interaction, its precise measurement could reveal deviations from the Standard Model of particle physics, potentially unlocking the door to new physics.

To explore this phenomenon, the Ricochet experiment was first proposed in 2017 and began its initial science phase in 2025 at the Institut Laue-Langevin (ILL), just 8.8 meters from a 58 MW thermal research nuclear reactor. This proximity provides an intense neutrino flux, ideal for studying CEvNS at low recoil energies (sub-keV).

Ricochet is a global collaboration involving about 50 physicists, engineers, and technicians from France, the U.S., Russia, and Canada. The center of the experiment is the CryoCube, an array of germanium-based cryogenic detectors cooled to 10 millikelvin. These detectors use a dual phonon-ionization readout, enabling them to distinguish CEνNS interactions from environmental backgrounds. With 18 detectors, each weighing about 42 grams, the experiment exposes a total germanium target mass of 0.75 Kg to a neutrino flux of approximately 10¹² neutrinos/cm²/s. The expected rate is few interactions per days in the Ricochet detectors. # At an energy threshold of 50 eVnr, the expected event rate is around 10 events per day.

A second science phase is envisioned, featuring the deployment of silicon target materials and a new detector technology called Q-Array, which uses superconducting target materials. These advancements will expand the experiment’s capabilities and increase the sensitivity to new physics in the CEvNS sector.