Comparing precise and accurate theoretical predictions for 6 He and 23 Ne beta decay observables with novel precision experiments

Multiple high precision β-decay measurements are being carried out these days on various nuclei, in search of beyond the standard model signatures. Among these nuclei are 6He and isotopes of Neon. These measurements necessitate very accurate standard model theoretical forecasts to be compared with. Motivated by the experimental surge, we present a general formalism for a precise calculation of β-decay observables, with controlled accuracy, based on a perturbative analysis of the theoretical observables related to the phenomena, including, e.g., high order nuclear recoil and shape corrections. The corrections' accuracy is analyzed by identifying a hierarchy of small parameters, related to the low momentum transfer characterizing β-decays. Concentrating on nuclei relevant to the ongoing experiments, we will examine highly accurate standard model numerical forecasts of the β-neutrino correlation coefficients and β-energy spectrum for 6He and 23Ne, compare them to existing as well as new measurements (the latter are conducted at SARAF accelerator, Israel), and get significant constraints on the standard model. Finally, we will discuss corrections resulting from the Coulomb interaction between the β particle and the nucleus, and their contribution to the analysis of those experiments.