Neutrinoless double beta decay, the inverted hierarchy, and precision determination ofθ12

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. *

Extracting Majorana properties from strong bounds on neutrinoless double beta decay

“…Although it becomes sizable when varying ∆m 2 s and θ s , the variation in δ M1 is much smaller than in δ M3 . In addition, the variation from mass splits, ∆m 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].…”

Neutrino-Less Double Beta Decay and Particle Physics

“…We would like to stress here that care has to be taken when different calculations are compared 54,55 : for instance, NMEs are made dimensionless by putting a factor 1/R…”

“…When two sensitivity expectations are given for one experiment they correspond to near and far time goals, see Table 4. Taken from 55 . most difficult physics goal related to this process i .…”

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

“…However, the contributions from the n > 0 modes and the SM neutrinos can JHEP07 (2011)103 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 [80], 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.…”