Nuclear deformation and neutrinoless double-$β$ decay of $^{94,96}$Zr, $^{98,100}$Mo, $^{104}$Ru, $^{110}$Pd, $^{128,130}$Te and $^{150}$Nd nuclei in mass mechanism

Abstract

The `β− β − ´0ν decay of 94,96 Zr, 98,100 Mo, 104 Ru, 110 Pd, 128,130 Te and 150 Nd isotopes for the 0 + → 0 + transition is studied in the Projected Hartree-Fock-Bogoliubov framework. In our earlier work, the reliability of HFB intrinsic wave functions participating in the β − β − decay of the above mentioned nuclei has been established by obtaining an overall agreement between the theoretically calculated spectroscopic properties, namely yrast spectra, reduced B(E2:0 + → 2 + ) transition probabilities, quadrupole moments Q(2 + ), gyromagnetic factors g(2 + ) as well as half-lives T 2ν 1/2 for the 0 + → 0 + transition and the available experimental data. In the present work, we study the `β− β − ´0ν decay for the 0 + → 0 + transition in the mass mechanism and extract limits on effective mass of light as well as heavy neutrinos from the observed half-lives T 0ν 1/2 (0 + → 0 + ) using nuclear transition matrix elements calculated with the same set of wave functions. Further, the effect of deformation on the nuclear transition matrix elements required to study the `β− β − ´0ν decay in the mass mechanism is investigated. It is noticed that the deformation effect on nuclear transition matrix elements is of approximately same magnitude in `β− β − ´2ν and `β− β − ´0ν decay.

Two-neutrino double beta decay of deformed nuclei within QRPA with realistic interaction

“…Recent result M 0ν = −1.61 obtained in Ref. [11] within the Projected Hartree-Fock-Bogoliubov approach is in a good agreement with the previous one of Ref. [10].…”

“…[17,18], deformation introduces a mechanism of suppression of the M 2ν GT matrix element that works even for the same initial and final deformations. The reduction gets even stronger when initial and final deformations differ from each other, and is mainly due to a decrease of the BCS overlap (11). The values of the overlap calculated with the realistic pairing interaction are very close to those obtained by using the constant pairing gap as in Refs.…”

Measurement of the Double Beta Decay Half-life of 150-Nd and Search for Neutrinoless Decay Modes with the NEMO-3 Detector

“…The suppression of the NME for 150 Nd has been estimated to be a factor 2.7 in the case of nuclear deformations derived from laboratory moments [12]. This increases the upper limit to m ν < 4.0 − 6.8 eV which is consistent with the limit derived using the NME of a pseudo SU(3) model [13] and the PHFB model [14], which also include the effect of nuclear deformation. Further progress in the calculation of the NME for 0νββ decay of 150 Nd is therefore urgently required.…”