Speaker
Description
Measurements in nuclear β decay played a crucial role in the development of the (V-A) theory of weak interactions, which is embedded in the standard electroweak model (SM). Experiments in β decay offer today a sensitive tool to search for physics beyond the SM, complementary to direct searches performed at high energies.
It has recently been observed that, in searches for new interactions and under very general assumptions, the determination of the so-called “Fierz interference term” in nuclear and neutron decays can potentially compete with searches at the LHC provided the sensitivity reaches a level below 10$^{−3}$ . This is because the Fierz term depends linearly on the exotic couplings whereas the cross sections for the production of new bosons depend quadratically. In nuclear and neutron decays the most direct and sensitive property to extract the Fierz term is the shape of the β energy spectrum.
This contribution presents recent precision measurements of β energy spectra in $^{6}$He and $^{20}$F decays performed at the National Superconducting Cyclotron Laboratory. A new technique that eliminates the very critical instrumental effect of back-scattering of electrons on detectors has been explored. The technique is being tested through the determination of the weak-magnetism contribution which can be accurately predicted in well selected transitions using the principle of Conservation of the Vector Current.
