gA -driven shapes of electron spectra of forbidden β decays in the nuclear shell model

Value of the Axial-Vector Coupling Strength in β and ββ Decays: A Review

“…actly the same computed shape for the two applied nuclear-model frameworks: the MQPM and the ISM [183]. The robustness of the β-spectrum shape against variations in g A and the calculational scheme makes the measurement of this spectrum interesting in terms of testing the basic framework of high-forbidden non-unique β decays.…”

“…3 for (highly) forbidden β transitions. It is also worth noting that in the works [182,183] several new experimentally interesting decays for the SSM treatment were discovered.…”

“…The value g V = 1.0 was assumed and the color coding represents the value of g A . Table 7 summarizes the exploratory works of [179,180,182,183] in terms of listing the studied decay-transition candidates and their potential for future measurements. Here only the studied non-unique β-decay transitions are listed since the unique forbidden transitions are practically g A -independent even when the next-to-leading-order terms are included in the β-decay shape factor [179].…”

Double β Decay and the Axial Strength

“…This makes SSM a robust tool for extracting information on the effective values of weak couplings. All the potentially interesting nuclei for the application of the spectrum-shape method found in Kostensalo et al [49] and Kostensalo and Suhonen [77] had mass numbers A = 87 − 115 and were second-, third-, or fourth-forbidden. In order to better understand the evolution of the quenching of g A it would be preferable to have also lighter and heavier nuclei to study.…”

“…The works [47,48] were continued by the works [49,77] where both the MQPM and ISM frameworks were used as theory tools. It was found that the spectrum shapes of the third-and fourthforbidden non-unique decays depend strongly on the value of g A , whereas the first-and second-forbidden decays were practically insensitive to the variations in g A .…”