0000000000122289
AUTHOR
M. T. Mustonen
Nuclear matrix elements for rare decays
Abstract Neutrinoless double electron capture ( 0 ν ECEC) is being vigorously investigated because of the possibility of it telling us something about the absolute mass scale of the neutrino. The resonant 0 ν ECEC is particularly interesting due to the potentially huge enhancement of its decay rate by a resonance condition. Recently the mass differences of two atom pairs were measured in order to study the enhancement of the 0 ν ECEC rates of 74Se and 112Sn. The associated nuclear matrix elements were also evaluated. The neutrino mass can also be detected by using beta decays with low Q values. Related to this we have investigated the second-forbidden decay branch of 115In with its ultra-lo…
MQPM description of the structure and beta decays of the odd Mo and Tc isotopes
The odd-mass isotopes A=95,97 of molybdenum are of interest for neutrino-physics applications. The microscopic quasiparticle-phonon model (MQPM) is used to calculate energy and decay characteristics of these nuclei and their beta-decay partners (Tc95 and Tc97). A realistic single-particle valence space and two-body interaction are used in the calculations. The computed results are compared with available data. The obtained energy spectra are also compared with earlier calculations. We present the first ever calculations for the rates of allowed and forbidden β+/EC decay transitions in these nuclei. In general our computed numbers agree rather well with the available data.
Microscopic quasiparticle–phonon description of beta decays of 113Cd and 115In using proton–neutron phonons
Abstract The fourth-forbidden non-unique ground-state-to-ground-state beta decays of 113 Cd and 115 In are calculated using a realistic microscopic two-body interaction and a realistic single-particle model space. To describe the involved initial and final nuclear states we introduce a proton–neutron variant of the microscopic quasiparticle–phonon model (MQPM), the proton–neutron MQPM (pnMQPM). The states of the pnMQPM are created by coupling quasiparticles with phonons of the proton–neutron quasiparticle random-phase approximation (pnQRPA). The computed half-lives and log f t values are found to be in excellent agreement with experimental data. Computed beta spectra of the decays are also …
Theoretical description of the fourth-forbidden non-unique β decays ofCd113andIn115
The half-lives and $\mathrm{log}\mathit{ft}$ values for the fourth-forbidden non-unique beta decays of the ground states of $^{113}\mathrm{Cd}$ and $^{115}\mathrm{In}$ were calculated using a transparent formulation for the ${\ensuremath{\beta}}^{\ensuremath{-}}$ transition amplitude. The microscopic quasiparticle-phonon model (MQPM) was used to calculate the initial and final states of the transitions. The corresponding wave functions were described as linear combinations of one- and three-quasiparticle configurations built in a realistic single-particle model space by using a realistic microscopic two-body interaction. The computed results for the $\mathrm{log}\mathit{ft}$ values and half…
Smallest KnownQValue of Any Nuclear Decay: The Rareβ−Decay ofIn115(9/2+)→Sn115(3/2+)
The ground-state-to-ground-state Q_{beta;{-}} value of ;{115}In was determined to 497.68(17) keV using a high-precision Penning trap facility at the University of Jyvaskyla, Finland. From this, a Q_{beta;{-}} value of 0.35(17) keV was obtained for the rare beta;{-} decay to the first excited state of ;{115}Sn at 497.334(22) keV. The partial half-life was determined to 4.1(6) x 10;{20} yr using ultra low-background gamma-ray spectrometry in an underground laboratory. Theoretical modeling of this 2nd-forbidden unique beta;{-} transition was also undertaken and resulted in Q_{beta;{-}} = 57_{-12};{+19} eV using the measured half-life. The discrepancy between theory and experiment could be attr…
Theoretical analysis of the possible ultra-low-Q-value decay branch of 135Cs
Abstract We have investigated the feasibility of observing an ultra-low- Q -value beta-decay branch of 135 Cs by applying the microscopic quasiparticle–phonon model with a realistic two-body nuclear interaction. This work was motivated by an earlier combined experimental and theoretical work on decays of 115 In. The inaccuracy of the ground-state-to-ground-state Q value limits our ability to draw definite conclusions, and therefore modern precision measurements for it are called for. We present the computed partial half-lives of each channel for the most likely ranges of Q values.