A Redetermination of the Neutrino Mass-Squared Difference in Tri-Maximal Mixing with Terrestrial Matter Effects

We re-fit for the neutrino mass-squared difference ∆m2 in the threefold maximal (ie. tri-maximal) mixing scenario using recent CHOOZ and SUPER-K data, taking account of matter effects in the Earth. While matter effects have little influence on reactor experiments and proposed long-baseline accelerator experiments with L ∼ 1000 km, they are highly significant for atmospheric experiments, suppressing naturally νe mixing and enhancing νμ − ντ mixing, so as to effectively remove the experimental distinction between threefold maximal and twofold maximal νμ − ντ mixing. Threefold maximal mixing is fully consistent with the CHOOZ and SUPER-K data and the best-fit value for the neutrino mass-squared difference is ∆m2 ≃ (0.98 ± 0.30 0.23 )× 10−3 eV2. To be published in Physics Letters B E-mail:[email protected] E-mail:[email protected] E-mail:[email protected]