Half-life Of 0νββ Decay Research Articles

Impact of recent updates to neutrino oscillation parameters on the effective Majorana neutrino mass in 0νββ decay

We investigate how recent updates to neutrino oscillation parameters and the sum of neutrino masses influence the sensitivity of neutrinoless double-beta (0νββ) decay experiments. Incorporating the latest cosmological constraints on the sum of neutrino masses and laboratory measurements on oscillations, we determine the sum of neutrino masses for both the normal hierarchy (NH) and the inverted hierarchy (IH). Our analysis reveals a narrow range for the sum of neutrino masses, approximately 0.06 eV/c2 for NH and 0.102 eV/c2 for IH. Utilizing these constraints, we calculate the effective Majorana masses for both NH and IH scenarios, establishing the corresponding allowed regions. Importantly, we find that the minimum neutrino mass is nonzero, as constrained by the current oscillation parameters. Additionally, we estimate the half-life of 0νββ decay using these effective Majorana masses for both NH and IH. Our results suggest that upcoming ton-scale experiments will comprehensively explore the IH scenario, while 100-ton-scale experiments will effectively probe the parameter space for the NH scenario, provided the background index can achieve 1 event/kton-year in the region of interest. Published by the American Physical Society 2024

Background study of the AMoRE-pilot experiment

We report a study on the background of the Advanced Molybdenum-Based Rare process Experiment (AMoRE), a search for neutrinoless double beta decay (0νββ) of 100Mo. The pilot stage of the experiment was conducted using ∼1.9 kg of 48deplCa100MoO4 crystals at the Yangyang Underground Laboratory, South Korea, from 2015 to 2018. We compared the measured β/γ energy spectra in three experimental configurations with the results of Monte Carlo simulations and identified the background sources in each configuration. We replaced several detector components and enhanced the neutron shielding to lower the background level between configurations. A limit on the half-life of 0νββ decay of 100Mo was found at T1/20ν≥3.0×1023 years at 90% confidence level, based on the measured background and its modeling. Further reduction of the background rate in the AMoRE-I and AMoRE-II are discussed.

New Limit for Neutrinoless Double-Beta Decay of ^{100}Mo from the CUPID-Mo Experiment.

The CUPID-Mo experiment at the Laboratoire Souterrain de Modane (France) is a demonstrator for CUPID, the next-generation ton-scale bolometric 0νββ experiment. It consists of a 4.2kg array of 20 enriched Li_{2}^{100}MoO_{4} scintillating bolometers to search for the lepton-number-violating process of 0νββ decay in ^{100}Mo. With more than one year of operation (^{100}Mo exposure of 1.17 kg×yr for physics data), no event in the region of interest and, hence, no evidence for 0νββ is observed. We report a new limit on the half-life of 0νββ decay in ^{100}Mo of T_{1/2}>1.5×10^{24} yr at 90% C.I. The limit corresponds to an effective Majorana neutrino mass ⟨m_{ββ}⟩<(0.31-0.54) eV, dependent on the nuclear matrix element in the light Majorana neutrino exchange interpretation.

Final Results of GERDA on the Search for Neutrinoless Double-β Decay.

The GERmanium Detector Array (GERDA) experiment searched for the lepton-number-violating neutrinoless double-β (0νββ) decay of ^{76}Ge, whose discovery would have far-reaching implications in cosmology and particle physics. By operating bare germanium diodes, enriched in ^{76}Ge, in an active liquid argon shield, GERDA achieved an unprecedently low background index of 5.2×10^{-4} counts/(keV kg yr) in the signal region and met the design goal to collect an exposure of 100kg yr in a background-free regime. When combined with the result of Phase I, no signal is observed after 127.2kg yr of total exposure. A limit on the half-life of 0νββ decay in ^{76}Ge is set at T_{1/2}>1.8×10^{26} yr at 90%C.L., which coincides with the sensitivity assuming no signal.

A comparative study of 0νββ decay in symmetric and asymmetric left-right model

We study the new physics contributions to neutrinoless double beta decay (0νββ) in a TeV scale left-right model with spontaneous D-parity breaking mechanism where the values of the SU(2)L and SU(2)R gauge couplings, gL and gR are unequal. Neutrino mass is generated in the model via gauge extended inverse seesaw mechanism. We embed the model in a non-supersymmetric SO(10) GUT with a purpose of quantifying the results due to the condition gL≠gR. We compare the predicted numerical values of half life of 0νββ decay, effective Majorana mass parameter and other lepton number violating parameters for three different cases; (i) for manifest left-right symmetric model (gL=gR), (ii) for left-right model with spontaneous D parity breaking (gL≠gR), (iii) for Pati-Salam symmetry with D parity breaking (gL≠gR). We show how different contributions to 0νββ decay are suppressed or enhanced depending upon the values of the ratio gRgL that are predicted from successful gauge coupling unification.

Read-out Electronics and Signal Processing in GERDA and Future Prospects

The GERDA experiment searches for the neutrinoless double beta decay of 76Ge. The experiment is using 36 kg of high-purity germanium detectors, simultaneously as source and detector, deployed into ultra-pure cryogenic liquid argon. GERDA is one the leading experiment in the field, reporting the highest sensitivity on the half-life of 0νββ decay with 1.1·1026 yr, the lowest background index with 6·10−4 cts/(keV·kg·yr) and an excellent energy resolution of 0.12% (FWHM). The search for the 0νββ decay of the isotope 76Ge will be continued in the next years by the LEGEND-200 experiment, that aims to reach a sensitivity up to 1027 yr using 200 kg of enriched HPGe detectors. The preparation of this experiment already started. The basic concepts of the GERDA read-out electronics, obeying both the severe requirements of ultra high radio-purity and cryogenic operation, are summarized. For LEGEND-200 a new electronics design, including a separation of the preamplifier in two stages, has been already designed and realized: results from tests are presented. Additionally, we will introduce the digital signal processing adopted for the energy reconstruction in GERDA and a new implementation of an optimum digital filter by means of the DPLMS method. This method are discussed and the first application to GERDA data are presented.

Experimental challenges in the measurement of double charge exchange reactions within the NUMEN project

The NUMEN project proposes to measure the absolute cross sections of heavy-ion induced Double Charge Exchange (DCE) reactions with the final goal to get information on the nuclear matrix elements involved in the neutrinoless double beta (0νββ) decay. The knowledge of the nuclear matrix elements is crucial to infer the neutrino average masses from the possible measurement of the half-life of 0νββ decay and also to compare experiments on different isotopes. DCE reactions and 0νββ decay present some similarities, the initial and final-state wave functions are the same and the transition operators are similar. Many challenges have to be faced for the experimental measurements of DCE reactions induced by heavy ions, since they are characterized by very low cross sections.

Experimental issues for the measurement of the double charge exchange reactions within the NUMEN project

The NUMEN project proposes to study heavy-ion induced Double Charge Exchange (DCE) reactions with the final goal to get information on the nuclear matrix elements for neutrinoless double beta (0νββ) decay. The knowledge of the nuclear matrix elements is crucial to infer the neutrino average masses from the possible measurement of the half-life of 0νββ decay. DCE reactions and 0νββ decay present some similarities, the initial and final-state wave functions are the same and the transition operators are similar. The experimental measurements of DCE reactions induced by heavy ions present a number of challenging aspects, since they are characterized by very low cross sections.

The GERDA experiment: results and perspectives

The Germanium Detector Array, GERDA, at Laboratori Nazionali del Gran Sasso (Italy), is designed to search for Majorana neutrinos via neutrinoless double beta (0νββ) decay of 76Ge. GERDA completed the Phase I in 2013, after an exposure of 21.6 kg·yr and with a background of about 0.01 cts/(keVkgyr): no signal was found and a limit on the half-life of T0ν1/2 > 2.1 · 1025 yr (90% C.L.) was established. The previous claim of 0νββ observation for 76Ge is strongly disfavoured in a model independent way. The commission for GERDA Phase II is currently ongoing and about 20 kg of additional enriched Ge diodes will be deployed. Pulse- shape analysis, together with the liquid argon instrumentation will allow to reach a background level one order of magnitude lower than in Phase I. In this paper the measurement of the half-life of 0νββ decay from GERDA Phase I and the expected sensitivity for Phase II are discussed.

Non-collapsing renormalized QRPA with proton-neutron pairing for neutrinoless double beta decay

Using the renormalized quasiparticle random phase approximation (RQRPA), we calculate the light neutrino mass mediated mode of neutrinoless double beta decay (0νββ-decay) of 76Ge, 100Mo, 128Te and 130Te. Our results indicate that the simple quasiboson approximation is not good enough to study the 0νββ-decay, because its solutions collapse for physical values of g pp. We find that extension of the Hilbert space and inclusion of the Pauli principle in the QRPA with proton-neutron pairing, allows us to extend our calculations beyond the point of collapse, for physical values of the nuclear force strength. As a consequence one might be able to extract more accurate values on the effective neutrino mass by using the best available experimental limits on the half-life of 0νββ-decay.