Motivating Zero Neutrino Mass Scale
New insight into the phenomenology of neutrino masses is suggested. Four ideas related to new neutrino physics considered: 1) Three absolute neutrino masses with zero smallest nu-mass are pointed out by geometric interpretation of SM hierarchies.
Note that in the SM without new physics all three neutrino masses are zero. The mass squared differences represent here new dynamical factors that deviate two neutrino masses m2 and m3 from zero values. Ina minimal neutrino mass model, based on neutrino oscillation mass squared differences, only two neutrino masses m2 and m3 must be different from zero. Zero value of the third neutrino mass also follows from oscillation physics; this time from maximal value of the atmospheric mixing angle and geometric nature of the SM hierarchies.2) As likely conjecture, minute neutrino masses cause the smallness of SM particle masses relative to the Plank mass scale.
Why are the magnitudes of SM Dirac masses chosen (by Nature) zero small in comparison with universal gravitation Plank mass scale? Why are the neutrino masses extraordinarily small even in comparison with other SM particle masses? These two questions (problems) must be connected to give substantial meaning to SM factual particle mass pattern. At present time of hidden, spontaneous violated, symmetries in physics the following conjecture seems appropriate: SM particle masses present one united particle mass System and zero neutrino mass scale is the primary cause of‘small’ size of known lepton and quark particle masses.It may be the right interpretation of the exceptionally small neutrino masses in the SM, a special ‘hint’ by Nature. Partially it is supported by the empirical feature that all mass hierarchies of SM Dirac particles are similar to the considered normal neutrino mass hierarchy, compare e.g. for charged leptons.
3) The origin of zero lightest neutrino mass is likely a result of Big Bang Anthropic Selection.
Zero neutrino mass value m1= 0 can be the result of Big Bang Anthropic Selection equally with the magnitudes of fine structure constant and other life-favored fundamental constants in our Universe. In that case the exceptionally small neutrino masses are one of the important anthropic relicts of the Big Bang. Since we are here, anthropic selection seems unavoidable, and it elucidates SM neutrino mass problem. Transition from the high energy Big Bang unification scale to low energy specialization scale is a necessary condition of anthropic selection since life would be impossible at the Plank mass scale. Much is still unknown on the origin of Big Bang at our Universe, but anthropic selection seems one of its attributes.
4) Characteristic neutrino mass sum Σmi = 0.06 eV is suggested as interesting observable quantity in cosmological, astrophysical and terrestrial experiments.