Speaker
Description
The precision measurement of the tritium β-decay spectrum provides a unique, model-independent window to search for physics beyond the Standard Model (SM). This research utilizes the framework of Generalized Neutrino Interactions (GNIs), which incorporates all theoretically allowed dimension-6 effective field theory (EFT) operators involving neutrinos. This approach generalizes the weak interaction beyond its standard V-A structure, accounting for both light neutrinos and additional heavier neutrino mass states.
Relativistic calculations demonstrate that the impact of GNIs on the electron energy spectrum can be parameterized by six fundamental spectral functions which depend on particle masses and coupling constants. Unlike the standard neutrino mass signature, which is localized near the endpoint, GNIs and sterile neutrinos can distort the shape of the entire spectrum.
To investigate these phenomena, we measured the tritium spectrum using a LiF crystal coupled to a cryogenic metallic magnetic calorimeter (MMC). This setup provides excellent energy resolution and access to the full spectrum, which is essential for identifying broad spectral distortions. Based on an analysis of a 10-day subset of the data, we derive constraints on effective GNI parameters involving both left- and right-handed neutrino currents.