Abstract
Assuming 3-ν mixing, neutrino oscillation explanation of the solar and atmospheric neutrino data and of the first KamLAND results, massive Majorana neutrinos and neutrinoless double-beta ((ββ)0ν-) decay generated only by the (V–A) charged current weak interaction via the exchange of the three Majorana neutrinos, we analyze in detail the possibility of determining the type of the neutrino mass spectrum by measuring of the effective Majorana mass |〈m〉| in (ββ)0ν-decay. The three possible types of neutrino mass spectrum are considered: (i) normal hierarchical (NH) m1⪡m2⪡m3, (ii) inverted hierarchical (IH), m1⪡m2≅m3, and (iii) quasi-degenerate (QD), m1≅m2≅m3, m1,2,3≳0.20 eV. The uncertainty in the measured value of |〈m〉| due to the imprecise knowledge of the relevant nuclear matrix elements is taken into account in the analysis. We derive the ranges of values of tan2θ⊙, θ⊙ being the mixing angle which controls the solar neutrino oscillations, and of the nuclear matrix element uncertainty factor, for which the measurement of |〈m〉| would allow one to discriminate between the NH and IH, NH and QD, and IH and QD spectra.
Highlights
The solar neutrino experiments Homestake, Kamiokande, SAGE, GALLEX/GNO, Super-Kamiokande (SK) and SNO [1, 2, 3, 4], the data on atmospheric neutrinos obtained by the Super-Kamiokande (SK) experiment [5] and the results from the KamLAND reactor antineutrino experiment [6], provide very strong evidences for oscillations of flavour neutrinos
Under the general and plausible assumptions of 3-ν mixing, neutrino oscillation explanation of the solar and atmospheric neutrino data, massive Majorana neutrinos and0ν -decay generated only by the (V-A) charged current weak interaction via the exchange of the three Majorana neutrinos, which will be assumed to hold throughout this study, the observation of0ν -decay can provide unique information on [27, 19, 21, 22, 32, 33] i) the type of neutrino mass spectrum which can be normal hierarchical (NH), inverted hierarchical (IH), or quasi-degenerate (QD), ii) on the absolute scale of neutrino masses, and [18, 19, 20, 21, 22, 23] iii) on the Majorana CP-violating phases α21 and α31
It is determined by the maximal values of |< m >| in the cases of NH and IH spectra and by the minimal values of |< m >| for the IH and QD spectra
Summary
Kamiokande (SK) and SNO [1, 2, 3, 4], the data on atmospheric neutrinos obtained by the Super-. Under the general and plausible assumptions of 3-ν mixing, neutrino oscillation explanation of the solar and atmospheric neutrino data, massive Majorana neutrinos and (ββ)0ν -decay generated only by the (V-A) charged current weak interaction via the exchange of the three Majorana neutrinos, which will be assumed to hold throughout this study, the observation of (ββ)0ν -decay can provide unique information on [27, 19, 21, 22, 32, 33] i) the type of neutrino mass spectrum which can be normal hierarchical (NH), inverted hierarchical (IH), or quasi-degenerate (QD), ii) on the absolute scale of neutrino masses, and [18, 19, 20, 21, 22, 23] iii) on the Majorana CP-violating phases α21 and α31. Under certain rather special conditions it might be determined in experiments with reactor νe [50]
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