6th Symposium on Neutrinos and Dark Matter in Nuclear Physics 2018

Neutrinoless ββ nuclear matrix elements using IVSD Jπ=2− data

Not scheduled

3m

IBS HQ, Daejeon, Korea

Poster

Speaker

Ms Lotta Jokiniemi (University of Jyväskylä)

Description

Ground-state-to-ground-state neutrinoless double beta ($0\nu \beta \beta$) decays in nuclei of current experimental interest are revisited. In order to improve the reliability of the nuclear matrix elements (NMEs) for the light Majorana-neutrino mode, the NMEs are calculated by exploiting the newly available data on isovector spin-dipole (IVSD) $J^{\pi }=2^{-}$ giant resonances obtained at RCNP, Osaka. In order to correctly describe the IVSD up to and beyond the giant-resonance region, the present computations are performed in extended no-core single-particle model spaces using the proton-neutron quasiparticle random-phase approximation (pnQRPA) with two-nucleon interactions based on the Bonn one-boson-exchange G matrix. The appropriate short-range correlations, nucleon form factors, higher-order nucleonic weak currents, and partial restoration of the isospin symmetry are included in the calculations. The results are compared with earlier calculations of Hyvärinen and Suhonen [Phys. Rev. C **91**, 024613 (2015)] performed in much smaller single-particle bases without access to the IVSD $J^{\pi }=2^{-}$ giant-resonance data reported here. The study offers a new way of fitting the $g_{ph}$ parameter of pnQRPA to the measured IVSD giant resonance instead of fitting it to the Gamow-Teller giant resonance in the traditional way. In fact, we study three different combinations to fit this parameter to available data and study the associated errors in the $0\nu \beta \beta$ NMEs.