title: Mikheyev-smirnov-wolfenstein effects in vacuum oscillations
abstract: We point out that for solar neutrino oscillations with the mass-squared difference of Deltam(2) approximately 10(-10)-10(-9) eV(2), i.e., in the so-called vacuum oscillation range, the solar matter effects are non-negligible, particularly for the low energy pp neutrinos. One consequence of this is that the values of the mixing angle straight theta and pi/2-straight theta are not equivalent, making it necessary to consider the entire physical range of the mixing angle 0</=straight theta</=pi/2 when determining the allowed values of the neutrino oscillation parameters.
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720 and Theory Group, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.initials: A
authors.lastname: Friedland