Electron spectra in forbidden β decays and the quenching of the weak axial-vector coupling constant gA
Kostensalo, J., Haaranen, M., & Suhonen, J. (2017). Electron spectra in forbidden β decays and the quenching of the weak axial-vector coupling constant gA. Physical Review C, 95(4), Article 044313. https://doi.org/10.1103/PhysRevC.95.044313
Published inPhysical Review C
© 2017 American Physical Society. Published in this repository with the kind permission of the publisher.
Evolution of the electron spectra with the effective value of the weak axial-vector coupling constant gA was followed for 26 first-, second-, third-, fourth- and fifth-forbidden β− decays of odd-A nuclei by calculating the involved nuclear matrix elements (NMEs) in the framework of the microscopic quasiparticle-phonon model (MQPM). The next-to-leading-order terms were included in the β-decay shape factor of the electron spectra. The spectrum shapes of third- and fourth-forbidden nonunique decays were found to depend strongly on the value of gA, while first- and second-forbidden decays were mostly unaffected by the tuning of gA. The gA-driven evolution of the normalized β spectra was found to be quite universal, largely insensitive to the small changes in the nuclear mean field and the adopted residual many-body Hamiltonian producing the excitation spectra of the MQPM. This makes the comparison of experimental and theoretical electron spectra, coined “the spectrum-shape method” (SSM), a robust tool for extracting information on the effective values of the weak coupling constants. In this exploratory work two new experimentally interesting decays for the SSM treatment were discovered: the ground-state-to-ground-state decays of 99Tc and 87Rb. Comparing the experimental and theoretical spectra of these decays could shed light on the effective values of gA and gV for second- and third-forbidden nonunique decays. The measurable decay transitions of 135Cs and 137Cs, in turn, can be used to test the SSM in different many-body formalisms. The present work can also be considered as a (modest) step towards solving the gA problem of the neutrinoless double beta decay. ...
PublisherAmerican Physical Society
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Kostensalo, Joel; Suhonen, Jouni (American Physical Society, 2017)The evolution of the shape of the electron spectra of 16 forbidden β− decays as a function of gA was studied using the nuclear shell model in appropriate single-particle model spaces with established, well-tested nuclear ...
COBRA collaboration (Elsevier, 2020)A dedicated study of the quenching of the weak axial-vector coupling strength gA in nuclear processes has been performed by the COBRA collaboration. This investigation is driven by nuclear model calculations which show ...
Kostensalo, Joel; Suhonen, Jouni (World Scientific Publishing Co. Pte. Ltd., 2018)The neutrinoless ββ decay of atomic nuclei continues to attract fervent interest due to its potential to confirm the possible Majorana nature of the neutrino, and thus the nonconservation of the lepton number. At the same ...
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