Low-energy neutrino experiments have quietly become precision tools for testing the Standard Model, the theory that describes all known particles and forces except gravity. This Letter shows that existing data are already sensitive to tiny quantum effects in how neutrinos interact, effects previously thought accessible only at giant accelerators.
Neutrinos are often called “ghost particles” because they almost never interact with matter. They stream through us in unimaginable numbers yet almost never leave a trace. Over the past decades, experimentalists have learned how to catch a tiny fraction of these elusive particles in the act, watching them scatter off electrons and, more recently, off entire atomic nuclei. Different experiments do this in different ways: some use neutrinos from nuclear reactors or particle accelerators, while others rely on solar neutrinos recorded by dark-matter detectors buried deep underground. Until now, however, each of these measurements has been studied largely on its own.
In this Letter, the authors bring all those strands together for the first time. By combining decades of data in a single, coherent framework, the work transforms a patchwork of individual experiments into a unified, high-precision test of the Standard Model. This global analysis allows the authors to pin down how “large” neutrinos appear to the electromagnetic force, the so-called neutrino charge radius, the only electromagnetic property that the Standard Model permits them to have, and at the same time to measure how strongly they couple to the weak force using only low-energy data.
The outcome is twofold. On the one hand, the Standard Model survives a remarkably stringent test: most of the room for exotic new interactions is now sharply constrained. On the other hand, the analysis reveals a small but intriguing deviation from the textbook prediction, a hint that is not yet conclusive but will be important to scrutinize with future measurements. In this sense, the work both tightens the net around possible new physics and points to where the next clues might emerge.
Beyond that, the study sets the stage for a new program: using increasingly sensitive low-energy neutrino and dark-matter detectors as precision instruments, capable of performing tests that once seemed to require only the highest-energy colliders. It offers a new reference point for ongoing and upcoming experiments and a clear roadmap for how “tabletop” neutrino measurements can continue to challenge our best theory of fundamental particles.
You can find the Letter at this link.
