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

Neutrino masses and mixing: Leptons versus Quarks

Comparison of properties of quark and leptons as well as understanding their similarities and differences is one of the milestones on the way to underlying physics. Several observations, if not accidental, can strongly affect the implications: (i) nearly tri-bimaximal character of lepton mixing, (ii) special neutrino symmetries, (iii) the QLC-relations. We consider possible connections between quarks and leptons which include the quark-lepton symmetry and unification, approximate universality, and quark-lepton complementarity. Presence of new neutrino states and their mixing with the left or/and right handed neutrinos can be the origin of additional differences of quarks and leptons.Comment: Latex, pdproc.sty, 19 pages, 3 figures, Talk given at the III International Workshop on: NO-VE "Neutrinos in Venice", Fifty years after the Neutrino discovery, 7-10 Feb 2006, Venice, Ital