Absolute values of neutrino masses: status and prospects

Abstract

Compelling evidences in favor of neutrino masses and mixing obtained in the last years in Super-Kamiokande, SNO, KamLAND and other neutrino experiments made the physics of massive and mixed neutrinos a frontier field of research in particle physics and astrophysics. There are many open problems in this new field. In this review we consider the problem of the absolute values of neutrino masses, which apparently is the most difficult one from the experimental point of view. We discuss the present limits and the future prospects of β-decay neutrino mass measurements and neutrinoless double-β decay. We consider the important problem of the calculation of nuclear matrix elements of neutrinoless double-β decay and discuss the possibility to check the results of different model calculations of the nuclear matrix elements through their comparison with the experimental data. We discuss the upper bound of the total mass of neutrinos that was obtained recently from the data of the 2dF Galaxy Redshift Survey and other cosmological data and we discuss future prospects of the cosmological measurements of the total mass of neutrinos. We discuss also the possibility to obtain information on neutrino masses from the observation of the ultra highenergy cosmic rays (beyond the GZK cutoff). Finally, we review the main aspects of the physics of core-collapse supernovae, the limits on the absolute values of neutrino masses from the observation of SN1987A neutrinos and the future prospects of supernova neutrino detection.1

Unification without low-energy supersymmetry

“…In order to obtain the correct values for the tau and top masses, we expect h 1 ∼ 0.1, g ∼ 1 and u 2 ∼ 100 GeV. Since F B ≃ M U /(4π) 2 , the mass of the light neutrino is then O (0.1 eV), consistent with the experimental constraints [4]. There is also a one-loop diagram that couples ν to N 1,2 but with the heavy B quark replaced by d. This diagram is comparable to the tree-level Dirac mass h 1 u 2 , so it does not qualitatively change the radiative see-saw mechanism.…”

Global constraints on absolute neutrino masses and their ordering

“…Indeed, the allowed values of m ββ are well below the 0νββ bounds in Eq. (13). Note that, in the right panel, there is no region allowed at 2σ, since the the global ∆χ 2 IO−NO exceeds 4 units.…”

“…In the left panel, both the NO and the IO allowed bands are horizontally cut at the m ββ values in Eq. (13). In the right panel, the upper bounds on m ββ are stronger in IO, and can be estimated by drawing in Fig.…”

Coherence and Wave Packets in Neutrino Oscillations

“…(4.20) and (4.21) with ∆m 2 kj = ∆m 2 (∆m 2 is the squared-mass difference and ϑ is the mixing angle; see the reviews in Refs. [12,41,52,13]). An incoherent average of the probability in the plane-wave approximation over a gaussian energy spectrum with width σ E reads…”