Neutrino mass matrix

It is assumed that the Dirac mass matrix for the neutrinos (..nu../sub e/,..nu../sub ..mu../,..nu../sub tau/) is similar in form to those for the quarks and charged leptons, and that the smallness of the observed ..nu.. masses results from the Gell-Mann--Ramond--Slansky mechanism. It is shown that if certain tentative experimental results concerning the ..nu.. masses and mixing angles are confirmed, significant limitations may be placed on the Majorana mass matrix. The most satisfactory simple assumption concerning the Majorana mass matrix is that it is approximately proportional to the Dirac mass matrix. Some general properties of the Dirac matrices are discussed.