The search for neutrinoless double beta decay

Abstract

In the last two decades the search for neutrinoless double beta decay has evolved into one of the highest priorities for understanding neutrinos and the origin of mass. The main reason for this paradigm shift has been the discovery of neutrino oscillations, which clearly established the existence of massive neutrinos. An additional motivation for conducting such searches comes from the existence of an unconfirmed, but not refuted, claim of evidence for neutrinoless double decay in 76 Ge. As a consequence, a new generation of experiments, employing different detection techniques and ββ isotopes, is being actively promoted by experimental groups across the world. In addition, nuclear theorists are making remarkable progress in the calculation of the neutrinoless double beta decay nuclear matrix elements, thus eliminating a substantial part of the theoretical uncertainties affecting the particle physics interpretation of this process. In this report, we review the main aspects of the double beta decay process and some of the most relevant experiments. The picture that emerges is one where searching for neutrinoless double beta decay is recognized to have both far-reaching theoretical implications and promising prospects for experimental observation in the near future. PACS 23.40.-s -β decay; double β decay; electron and muon capture. PACS 14.60.Pq -Neutrino mass and mixing.

Effective Majorana mass and neutrinoless double beta decay

“…In reality, the total efficiency, the energy resolution, the atomic mass and the isotopic fraction of the considered isotopes have to be considered, too. A complete review of the topic is given in [23,24].…”

Operation and first results of the NEXT-DEMO prototype using a silicon photomultiplier tracking array

“…The detector boasts two important features for β β 0ν searches: excellent energy resolution (better than 1% FWHM at the Q value of 136 Xe) and event topological information for the identification of signal and background. This combination gives NEXT an excellent experimental sensitivity to β β 0ν searches [2]. In addition, the technique can be extrapolated to the ton-scale, thus allowing the full exploration of the inverted hierarchy of neutrino masses [3].…”

Backgrounds and sensitivity of the NEXT double beta decay experiment

“…Evidence of this process would establish that massive neutrinos are Majorana particles, provide a hint of a new physics scale beyond the Standard Model and prove the violation of total lepton number, a key element to explain the observed asymmetry between matter and antimatter in the universe. In addition, the measurement of the ββ0ν-decay rate would provide information on the absolute scale of neutrino masses [1], as shown in Eq.1:…”

“…As in other rare * Corresponding author e-mail: miquel.nebot@ific.uv.es event detectors, backgrounds of cosmogenic origin and natural radioactivity from materials are a problem, and thus underground operation and selection of radiopure materials is essential. In this sense additional experimental features are desired to improve the sensitivity of the detector, such as extra background (B) rejection, better detector efficiency ( ) or larger exposure (M • t) [1]. This relation can be summarized as follows :…”