Elements of the neutrino mass matrix: Allowed ranges and implications of texture zeros

We study the range of the elements of the neutrino mass matrix m(nu) in the charged lepton basis. Neutrinoless double beta decay is sensitive to the ee element (the effective mass) of m(nu). We then analyze the phenomenological implications of single texture zeros. In particular, interesting predictions for the effective mass can be obtained, in the sense that typically only little cancellation due to the Majorana phases is expected. Some cases imply constraints on the atmospheric neutrino mixing angle.