Comparison of Microscopic Interacting Boson Model and Quasiparticle Random Phase Approximation 0νββ Decay Nuclear Matrix Elements

Jenni Kotila

doi:10.3389/fspas.2021.652180

Abstract

The fundamental nature of the neutrino is presently a subject of great interest. A way to access the absolute mass scale and the fundamental nature of the neutrino is to utilize the atomic nuclei through their rare decays, the neutrinoless double beta (0νββ) decay in particular. The experimentally measurable observable is the half-life of the decay, which can be factorized to consist of phase space factor, axial vector coupling constant, nuclear matrix element, and function containing physics beyond the standard model. Thus reliable description of nuclear matrix element is of crucial importance in order to extract information governed by the function containing physics beyond the standard model, neutrino mass parameter in particular. Comparison of double beta decay nuclear matrix elements obtained using microscopic interacting boson model (IBM-2) and quasiparticle random phase approximation (QRPA) has revealed close correspondence, even though the assumptions in these two models are rather different. The origin of this compatibility is not yet clear, and thorough investigation of decomposed matrix elements in terms of different contributions arising from induced currents and the finite nucleon size is expected to contribute to more accurate values for the double beta decay nuclear matrix elements. Such comparison is performed using detailed calculations on both models and obtained results are then discussed together with recent experimental results.

Highlights

The question of whether neutrinos are Majorana or Dirac particles and what is the neutrino mass parameter remains one of the most fundamental problems in physics today
The 0νββ decay experiments aim to obtain the half-life of the process and Comparison of IBM-2 and quasiparticle random phase approximation (QRPA) 0νββ NMEs information to be extracted from the experiments is subject to uncertainties arising from the uncertainties in the related nuclear matrix elements (NMEs)
NMEs are multiplied by nuclear radius in fm, R = R0A1/3, with R0 = 1.2 fm in order to make them dimensionless, which is the way they are usually quoted

Summary

Introduction

The question of whether neutrinos are Majorana or Dirac particles and what is the neutrino mass parameter remains one of the most fundamental problems in physics today. Observation of neutrinoless double beta decay (0νββ), hypothesized extremely rare second-order process of weak interaction, would verify the Majorana nature of the neutrino, constrain the absolute scale of the neutrino mass spectrum, and provide proof of lepton-number violation. It would have fundamental implications for neutrino physics, theories beyond the standard model, and cosmology. The reliable calculation of these NMEs is of utmost importance

Results

Discussion

Conclusion