Neutrinoless Double Beta Decay, the Inverted Hierarchy and Precision Determination of theta(12)

Abstract

Ruling out the inverted neutrino hierarchy with neutrinoless double beta decay experiments is possible if a limit on the effective mass below the minimal theoretically possible value is reached. We stress that this lower limit depends strongly on the value of the solar neutrino mixing angle: it introduces an uncertainty of a factor of 2 within its current 3σ range. If an experiment is not background-free, a factor of two in effective mass corresponds to a combined factor of 16 improvement for the experimental parameters running time, detector mass, background level and energy resolution. Therefore, a more precise determination of θ 12 is crucial for the interpretation of experimental results and the evaluation of the potential and requirements for future experiments. We give the required half-lifes to exclude (and touch) the inverted hierarchy regime for all double beta decay isotopes with a Q-value above 2 MeV. The nuclear matrix elements from 6 different groups and, if available, their errors are used and compared. We carefully put the calculations on equal footing in what regards various convention issues. We also use our compilation of matrix elements to give the reachable values of the effective mass for a given half-life value.

Neutrino Physics with JUNO

“…3-2). In a backgrounddominated neutrinoless double beta decay experiment, a factor of two improvement in the effective mass sensitivity corresponds to a combined factor of 16 improvement for the experimental parameters of the running time, detector mass, background level and energy resolution [119,120]. Therefore, the precision measurement of sin 2 θ 12 is crucial for the next generation of the neutrinoless double beta decay experiments, which aim to cover the whole parameter space corresponding to IH.…”

Extracting Majorana Properties in the Throat of Neutrinoless Double Beta Decay

“…The same thing happens for the lower limit of m ee [46]. For inverted hierarchy (IH), the effective mass m ee cannot vanish.…”

“…The effect of θ r and θ s uncertainties on 0ν2β decay can be found in [45] and [46]. With the reactor angle θ r being precisely measured [50,53], the major uncertainty now mainly comes from the solar angle θ s [46,48].…”

“…The effect of θ r and θ s uncertainties on 0ν2β decay can be found in [45] and [46]. With the reactor angle θ r being precisely measured [50,53], the major uncertainty now mainly comes from the solar angle θ s [46,48]. The next-generation of reactor neutrino experiments with medium baseline, such as JUNO [54] and RENO-50 [55] experiments can have very precise measurement on θ s , with relative uncertainty down to ∼ 0.3% [54,56].…”

Neutrino mass and μ → e + γ from a mini-seesaw

“…However, the contributions from the n > 0 modes and the SM neutrinos can add constructively, so the total rate can be larger if c is such that the KK contribution dominates the zero-mode. Given the potential experimental reach for an inverted mass hierarchy [38], the additional contribution from the KK neutrinos can improve the prospects for 0νββ-decay observation. Let us emphasize, however, that the SM contribution will typically dominate the KK contribution in the region of parameter space where the largest KK contribution comes from the zero-mode.…”