S.T. Petcov

On pseudo-Dirac neutrinos, neutrino oscillations and neutrinoless double β-decay

The characteristic features of the models of neutrino mixing containing onlu pseudo-Dirac massive neutrinos are discussed in the case of negligible neutrino splitting. In this approximation the massive neutrinos appear to be Dirac particles possessing nonstandard magnetic moments. However, the neutrinoless double β-decay as well as all other processes usually associated with the existence of massive Majorana neutrinos are allowed.

On the MSW effect with massless neutrinos and no mixing in the vacuum

Abstract The general properties of the resonantly enhanced neutrino transitions in matter induced by neutrino flavour changing neutral current (FCNC) interactions (rather than by nontrivial neutrino mixing in vacuum) are analysed. Such transitions can take place even if neutrinos have zero mass. It is shown, in particular, that matter-enhanced transitions of the solar neutrinos (into ντ, for instance) generated by neutrino FCNC interactions are not excluded by the existing data and provide an alternative solution of the solar neutrino problem.

Resonance Amplification and t Violation Effects in Three Neutrino Oscillations in the Earth

Abstract The matter effects in three-neutrino oscillations in a beam of neutrinos passing through the earth are discussed. An exact analytic expression for the T-violating asymmetry in oscillations involving the three flavour neutrinos in matter with constant density is derived and it is shown that this asymmetry can be amplified considerably by matter. In particular, the T-violating asymmetry in the oscillations of neutrinos which have passed through the earth can be much larger than the analogous asymmetry in the oscillations in vacuum.

Update of the solar neutrino oscillation analysis with the 766 Ty KamLAND spectrum

Abstract We investigate the impact of the 766.3 Ty KamLAND spectrum data on the determination of the solar neutrino oscillation parameters. We show that the observed spectrum distortion in the KamLAND experiment firmly establishes Δ m 21 2 to lie in the low-LMA solution region. The high-LMA solution is excluded at more than 4σ by the global solar neutrino and KamLAND spectrum data. The maximal solar neutrino mixing is ruled out at 6σ level. The 3σ allowed region in the Δ m 21 2 – sin 2 θ 12 plane is found to be remarkably stable with respect to leaving out the data from one of the solar neutrino experiments from the global analysis. We perform a three flavor neutrino oscillation analysis of the global solar neutrino and KamLAND spectrum data as well. The 3σ upper limit on sin 2 θ 13 is found to be sin 2 θ 13 0.055 . We derive predictions for the CC to NC event rate ratio and day–night (D–N) asymmetry in the CC event rate, measured in the SNO experiment, and for the suppression of the event rate in the BOREXINO and LowNu experiments. Prospective high precision measurements of the solar neutrino oscillation parameters are also discussed.

Heavy Higgs bosons at LEP

Production of a heavy Weinberg–Salam-type neutral Higgs boson at LEP energies is considered. We conclude that the Higgs is unlikely to be detected at LEP if its mass is greater than 150 GeV.

Constraints from neutrino oscillation experiments on the effective Majorana mass in neutrinoless double beta decay

Abstract We determine the possible values of the effective Majorana neutrino mass |〈m〉|=| ∑ j U ej 2 m j | in the different phenomenologically viable three and four-neutrino scenarios. The quantities U αj ( α = e , μ , τ ,…) denote the elements of the neutrino mixing matrix and the Majorana neutrino masses m j ( j =1,2,3,…) are ordered as m 1 2 Assuming m 1 ≪ m 3 in the three-neutrino case and m 1 ≪ m 4 in the four-neutrino case, we discuss, in particular, how constraints on |〈 m 〉| depend on the mixing angle relevant in solar neutrino oscillations and on the three mass-squared differences obtained from the analyses of the solar, atmospheric and LSND data. If neutrinoless double β -decay proceeds via the mechanism involving |〈 m 〉|, conclusions about neutrinoless double β -decay can be drawn. If one of the two viable four-neutrino schemes (Scheme A) is realized in nature, |〈 m 〉| can be as large as 1 eV and neutrinoless double β -decay could possibly be discovered in the near future. In this case a Majorana CP phase of the mixing matrix U could be determined. In the other four-neutrino scheme (Scheme B) there is an upper bound on |〈 m 〉| of the order of 10 −2 eV. In the case of three-neutrino mixing the same is true if the neutrino mass spectrum is hierarchical, however, if there exist two quasi-degenerate neutrinos and the first neutrino has a much smaller mass, values of |〈 m 〉| as large as ∼0.1 eV are possible.

Remarks on the Zee model of neutrino mixing (μ →e+ γ, νH→ νL + γ, etc.)

Abstract Some features of the Zee model of lepton number nonconservation are discussed. In particular, the predictions of the model for the μ →e+ γ decay rate and the neutrino radiative life-times (ν H → ν L + γ) are analyzed in detail.

Precision neutrino oscillation physics with an intermediate baseline reactor neutrino experiment

We discuss the physics potential of intermediate

Exact analytic description of two-neutrino oscillations in matter with exponentially varying density

Lensuremath{sim}20char21{}30mathrm{km}

On the Analytic Description of Two Neutrino Transitions of Solar Neutrinos in the Sun

baseline experiments at reactor facilities. Assuming that the solar neutrino oscillation parameters