Riddle of the Neutrino Mass

We discuss some known approaches and results as well as few new ideas concerning origins and nature of neutrino mass. The key issues include (i) connections of neutrino and charged fermions masses, relation between masses and mixing, energy scale of new physics behind neutrino mass where possibilities spread from the Planck and GUT masses down to a sub-eV scale. The data hint two different new physics involved in generation of neutrino mass. Determination of the CP phase as well as mass hierarchy can play important role in identification of new physics. It may happen that sterile neutrinos provide the key to resolve the riddle.Comment: 6 pages, talk given at the Neutrino Oscillation Workshop, NOW 2014, Conca Specchiulla (Otranto, Lecce, Italy), September 7 - 14, 201

Solar Neutrinos and Lepton Mixing

With latest experimental data the solar neutrino problem enters new phase when crucial aspects of the problem can be formulated in an essentially (solar) model independent way. Original neutrino fluxes can be considered as free parameters to be found from the solar neutrino experiments. Resonance flavour conversion gives the best fit of all experimental results. Already existing data allow one to constraint both the neutrino parameters and the original neutrino fluxes. The reconciliation of the solution of the solar neutrino problem with other neutrino mass hints (atmospheric neutrino problem, hot dark matter etc.) may require the existence of new very light singlet fermion. Supersymmetry can provide a framework within which the desired properties of such a light fermion follow naturally. The existence of the fermion can be related to axion physics, mechanism of $\mu$-term generation etc..Comment: 9 pages, LaTeX, no figures. Talk given at the XXXth Rencontres de Moriond on Electroweak and Unified Theories, Les Arcs, Savoie - France, March 11 - 18, 199

Searches for sterile neutrinos with IceCube DeepCore

We show that study of the atmospheric neutrinos in the 10--100 GeV energy range by DeepCore sub-array of the IceCube Neutrino Observatory can substantially constrain the mixing of sterile neutrinos of mass $\sim 1$ eV with active neutrinos. In the scheme with one sterile neutrino we calculate $\nu_\mu-$ and $\bar{\nu}_\mu-$ oscillation probabilities as well as zenith angle distributions of $\nu_\mu^{CC}$ events in different energy intervals in DeepCore. The distributions depend on the mass hierarchy of active neutrinos. Therefore, in principle, the hierarchy can be identified, if $\nu_s$ exists. After a few years of exposure the DeepCore data will allow to exclude the mixing $|U_{\mu 4}|^2 \geq 0.02$ indicated by the LSND/MiniBooNE results. Combination of the DeepCore and high energy IceCube data will further improve sensitivity to $\nu_s$ mixing parameters.Comment: PDFLaTeX, 6 pages, 6 PDF figures, minor comments added, accepted in Phys. Rev.