Chasing CHOOZ

Since 1998 when SuperKamiokande announced incontrovertible evidence of neutrino oscillations, a series of experiments have unravelled most of the fundamental neutrino parameters. Two important pieces of information still await determination: the absolute value of the masses, together with their hierarchy, and the third mixing angle, for which there only exists a limit set by the CHOOZ experiment. From the theoretical side, neutrino masses are hardly surprising in the context of the grand unified[1, 2, 3, 4] generalizations of the Standard Model. While some of us predicted one large mixing angle in the MNS lepton mixing matrix, the recent determination of two large mixing angles comes as a surprise, and poses unforeseen theoretical challenges. In the following we offer several remarks as to the theoretical implications of the present data set and note that with a modest infusion of grand unification ideas, it is possible to relate the CKM and MNS matrices. In a wide class of models, the CHOOZ angle is even predicted in terms of the Cabibbo angle.