0νββnuclear matrix elements and the occupancy of individual orbits

Abstract

The measured occupancies of valence orbits in 76 Ge and 76 Se are used as a guideline for modification of the effective mean field energies that results in better description of these quantities. With them, in combination with the self-consistent renormalized quasiparticle random phase approximation (SRQRPA) method that ensures conservation of the mean particle number in the correlated ground state, we show that the resulting 0νββ nuclear matrix element for the 76 Ge → 76 Se transition is reduced by ∼25% compared to the previous QRPA value, and therefore the difference between the present approach and the interacting shell model predictions becomes correspondingly smaller. Analogous modification of the mean field energies for the A = 82 system also results in a reduction of 0νββ matrix element for the 82 Se → 82 Kr transition, making it also closer to the shell model prediction.

Valence neutron properties relevant to the neutrinoless double-βdecay of130Te

“…When the calculations were modified they substantially reduced the uncertainty in the various calculations e.g. [7][8][9][10]. In 130 Te→ 130 Xe, the subject of one of the major experiments under way searching for this exotic decay mode, we again find that the valence orbits participate substantially differently from what is in the existing QRPA and shell-model calculations.…”

“…Neutron pairing correlations were studied at the same time indicating no breaking of the BCS description of the ground state [6]. Within the QRPA framework, subsequent calculations for 76 Ge with an adjusted mean field led to a reduction of the matrix element M 0ν by ∼20-30% [7][8][9]. Calculations using the shell model with modified interactions found a 15% increase in the nuclear matrix elements [10].…”

Theoretical mean-field and experimental occupation probabilities in the double-βdecay systemGe76toMoreno1, Guerra2, Sarriguren3 et al. 2010Phys. Rev. CSelf Cite14160View full textAdd to dashboardCite

“…this failure is shared by a large variety of the Skyrme forces where the Skyrme spin-orbit strength W 0 is equal for protons and neutrons. In any case, the self-consistent deformed single nucleon potential gives better agreement with experiment for the occupation probabilities than a Woods-Saxon potential [3,4].…”

“…By increasing the binding energy of the 0g 9/2 level, the agreement is better, because its occupation probability increases and eventually reaches the experimental one. This energy shifting has been performed by hand in previous works [3][4][5] to obtain the experimental occupation probabilities, and the resulting ground-state structure has been used to compute neutrinoless double-β matrix elements. Shell-model calculations [6] have also been carried out with occupation probabilities in good agreement with experimental ones, but the single-particle energies used are not available in the literature.…”

Possibility of measuring theCPMajorana phases in0νββdecay

“…Complementary experimental information from related processes like the 2νββ-decay [46], charge-exchange [49] and particle transfer reactions [50] is also very important. The differences between the results of various nuclear structure approaches could be understood by performing an anatomy of the 0νββ-decay NME [35,38,51] . The recent development in the field is very encouraging.…”