Matter effects on neutrino oscillations in long baseline experiments - art. no. 053017

We calculate matter effects on neutrino oscillations relevant for long base line experiments. In particular, we compare the results obtained with const ant density along the neutrino path versus results obtained by incorporatin g the actual density profiles in the Earth. We study the dependence of the oscillation signal on both E/Delta m(atm)(2) and on the angles in the lepto nic mixing matrix. We also comment on the influence of Delta m(sol)(2) and CP violation on the oscillations. The results show quantitatively how, as a function of these input parameters, matter effects can cause significant ( 25%) changes in the oscillation probabilities. An important conclusion is t hat matter effects can be useful in amplifying certain neutrino oscillation signals and helping one to obtain measurements of mixing parameters and th e magnitude and sign of Delta m(atm)(2).