2023/12/12 by M. Ramalho, Ramalho, Marlom, J. Suhonen +1
Physics and Astronomy · #Nuclear physics research studies #Neutrino Physics Research #Quantum Chromodynamics and Particle Interactions
paper · pdf · doi:10.48550/arxiv.2312.07448
In the present paper we treat the second-forbidden non-unique (2nd-nu) ground-state-to-ground-state β- decay 99\textrmTc(9/2+)→ 99\textrmRu(5/2+), with a 100% branching ratio, within the framework of the nuclear shell model (NSM). The energy spectrum of the electrons emitted in this β-decay transition (β-electron spectrum) is sensitive to the wave functions of the involved initial (9/2+) and final (5/2+) nuclear ground states through the many involved nuclear matrix elements (NME). The β-electron spectrum of this transition is potentially indicative of the effective value, g\rm A\rm eff, of the weak axial coupling, g\rm A, of crucial importance for extraction of information on beyond-the-standard-model physics from the results of the present and future rare-events experiments. We describe the β spectral shape of this decay by using a state-of-the-art β-decay formalism and compute the many involved NME using the well established NSM Hamiltonians jj45pnb and glekpn. We have found a strong dependence of the β spectral shape on the value of g\rm A making it a good candidate for determination of the value of g\rm A\rm eff through comparison with the corresponding experimental β spectral shape. We have also found an interesting dependence of the β spectral shape on the value of the so-called small relativistic vector NME, sNME, used to match the computed half-life with the measured one.