18-detector neutrino system probes rare particle interactions near nuclear reactor

MIT researchers working on an international neutrino experiment have expanded its detector setup from two devices to 18 while developing software to automate monitoring and analysis of the growing system.

The work is part of Ricochet, an international experiment studying neutrinos produced by a nuclear reactor at the Institut Laue-Langevin in Grenoble, France. MIT PhD student Faith Reyes is part of the collaboration and has helped manage the detector system as it expanded.

Ricochet is designed to observe coherent elastic neutrino-nucleus scattering, a low-energy interaction in which a neutrino scatters off an entire atomic nucleus. Studying the process could help researchers better understand neutrino properties and probe questions that the Standard Model of particle physics does not fully answer.

Neutrinos are extremely difficult to detect because they have very little mass and rarely interact with matter. They are produced in processes including radioactive decay inside nuclear reactors, making reactors useful sources for experiments designed to study their behavior.

Eighteen detectors raise complexity

Reyes initially joined Ricochet expecting to work on a project based at MIT. When it became clear that the project would not be ready within the timeframe of her PhD, she shifted her attention to the detector work underway in France.

During her first three-month visit, Ricochet was operating two detectors. Reyes spent much of that period performing routine tasks needed to understand their performance and operation.

The experiment subsequently expanded to nine detectors and eventually 18. That growth also increased the amount of repetitive work required to monitor the equipment and analyze the data being generated.

Reyes and a colleague responded by developing a software framework capable of automating much of the low-level analysis and detector monitoring that had previously been performed manually.

“It’s sort of like you’re building your own stuff to replace yourself,” Reyes said. “Which is nice in a way because you can save yourself a lot of time.”

Working directly with the detectors and building the software gave Reyes a detailed understanding of how the experiment operates. Her role also evolved from learning the system to helping other researchers work with it.

“It felt like my collaborators trusted me, and I had something of value to give to the collaboration,” she said.

Rare scattering tests physics

Ricochet’s scientific target is particularly difficult to study because neutrinos interact so weakly with ordinary matter. The experiment uses neutrinos generated by a nuclear reactor to investigate coherent elastic neutrino-nucleus scattering at low energies.

Such measurements could provide another way to examine the Standard Model, which accurately describes many known fundamental particles and forces but does not provide a complete description of nature.

“The Standard Model is extremely accurate and describes most of everything that we see,” Reyes said. “But it’s not complete.”

The detector work has also turned into a larger international effort for Reyes. She has made multiple research visits to France, including a nine-month stay through the Chateaubriand Fellowship, allowing her to work directly alongside other Ricochet researchers.

Reyes plans to continue research after completing her doctorate and is considering a postdoctoral position. For now, the expanded Ricochet detector system and the tools developed to operate it are helping researchers pursue one of particle physics‘ hardest-to-observe interactions.