Extracting Majorana Properties in the Throat of Neutrinoless Double Beta Decay

Assuming that neutrinos are Majorana particles, we explore what information can be inferred from future strong limits (i.e. non-observation) for neutrinoless double beta decay. Specifically we consider the case where the mass hierarchy is normal and the different contributions to the effective mass $\langle m \rangle_{ee}$ partly cancel. We discuss how this fixes the two Majorana CP phases simultaneously from the Majorana Triangle and how it limits the lightest neutrino mass $m_1$ within a narrow window. The two Majorana CP phases are in this case even better determined than in the usual case for larger $\langle m \rangle_{ee}$. We show that the uncertainty in these predictions can be significantly reduced by the complementary measurement of reactor neutrino experiments, especially the medium baseline version JUNO/RENO-50. We also estimate the necessary precision on $\langle m \rangle_{ee}$ to infer non-trivial Majorana CP phases and the upper limit \langle m \rangle_{ee} \lesssim 1\,\mbox{meV} sets a target for the design of future neutrinoless double beta decay experiments.Comment: 21 pages, 10 figure

JUNO and Neutrinoless Double Beta Decay

We study the impact of the precision determination of oscillation parameters in the JUNO experiment on half-life predictions for neutrinoless double beta decay. We show that the solar neutrino mixing angle can be measured by JUNO with below 1% uncertainty. This implies in particular that the minimal value of the effective mass in the inverted mass ordering will be known essentially without uncertainty. We demonstrate that this reduces the range of half-life predictions in order to test this value by a factor of two. The remaining uncertainty is caused by nuclear matrix elements. This has important consequences for future double beta decay experiments that aim at ruling out the inverted mass ordering or the Majorana nature of neutrinos.Comment: 11 pages, 7 figure

Half-life Expectations for Neutrinoless Double Beta Decay in Standard and Non-Standard Scenarios

We investigate the half-life expectations for neutrinoless double beta decay by applying statistical distributions of neutrino mixing observables, neutrino mass constraints from cosmology and nuclear matrix elements. The analysis is performed in the standard scenario of active Majorana neutrino exchange, when light sterile neutrinos are added, and within TeV-scale left-right symmetric frameworks. The latter two cases correspond to a modified phenomenology of double beta decay for a normal and inverted mass ordering, and thus different discovery potential for future experiments.Comment: 18 pages, 10 figures, and 4 table

New physics effects on neutrinoless double beta decay from right-handed current

We study the impact of new physics contributions to neutrinoless double beta decay arising from right-handed current in comparison with the standard mechanism. If the light neutrinos obtain their masses from Type-II seesaw within left-right symmetric model, where the Type-I contribution is suppressed to negligible extent, the right-handed PMNS matrix is the same as its left-handed counterpart, making it highly predictable and can be tested at next-generation experiments. It is very attractive, especially with recent cosmological constraint favoring the normal hierarchy under which the neutrinoless double beta decay is too small to be observed unless new physics appears as indicated by the recent diboson excess observed at ATLAS. The relative contributions from left- and right-handed currents can be reconstructed with the ratio between lifetimes of two different isotopes as well as the ratio of nuclear matrix elements. In this way, the theoretical uncertainties in the calculation of nuclear matrix elements can be essentially avoided. We also discuss the interplay of neutrinoless double beta decay measurements with cosmology, beta decay, and neutrino oscillation.Comment: 10 pages, 5 figure

The Leptonic CP Phase from T2(H)K and Muon Decay at Rest

Combining neutrino oscillations at T2K or T2HK with antineutrinos oscillations from muon decay at rest (DAR) allows a determination of the leptonic CP-violating phase delta. The degeneracies of this phase with theta13 and theta23 are broken and delta can be reliably distinguished from 180-delta. We present the sensitivity to delta of T2(H)K together with a muon DAR experiment using Super-K as a near detector and Hyper-K at the Tochibora site as a far detector.Comment: 24 pages, 8 figures, v2 Includes CCQE and nu-e elastic background