First-forbidden transition of nuclear β decay by projected shell model

Abstract

The first-forbidden transition of nuclear β decay is expected to play crucial roles in many aspects in nuclear physics, nuclear astrophysics and particle physics such as the stellar β-decay rates and the reactor anti-neutrino spectra. In this work we develop the projected shell model (PSM) for description of first-forbidden transition of nuclear β decay for the first time. Detailed theoretical framework and logics are provided, and 35 dominant first-forbidden transitions that are expected to be important for the reactor anti-neutrino spectra problems are calculated and compared systematically with the data to test the new development of the PSM. The corresponding experimental Logf0t values are described reasonably, and the quenching factors of nuclear matrix elements are found to affect the Logf0t values as well as the related shape factors, which may be helpful for better understanding of the reactor anti-neutrino spectra problems.