Four-neutrino MS2 mixing

We present a simple scheme of mixing of four neutrinos that can accommodate the results of all neutrino oscillation experiments, the observed abundanc es of primordial elements produced in Big-Bang Nucleosynthesis and the curr ent upper bound for the effective Majorana neutrino mass in neutrinoless do uble-beta decay (assuming that massive neutrinos are Majorana particles). T he scheme has maximal mixing in the nu(mu),nu(tau)-nu(3),nu(4) sector and s mall mixings in the nu(e),nu(s)-nu(1),nu(2) and nu(e),nu(mu)-nu(1),nu(3) (o r nu(e),nu(mu)-nu(1),nu(4)) sectors (MS2). We discuss the implications of t his scheme for short and long baseline oscillation experiments and for neut rinoless double-beta decay and tritium beta-decay experiments. (C) 1999 Els evier Science B.V. All rights reserved.