Testing matter effects in very long baseline neutrino oscillation experiments

Assuming three-neutrino mixing, we study the capabilities of very long base line neutrino oscillation experiments to verify and test the MSW effect and to measure the lepton mixing angle theta(13) We suppose that intense neutr ino and antineutrino beams will become available in so-called neutrino fact ories. We find that the most promising and statistically significant result s can be obtained by studying nu(e) --> nu(mu) and <(nu)over bar>(e) --> <( nu)over bar>(mu) oscillations which lead to matter enhancements and suppres sions of wrong sign muon rates. We show the theta(13) ranges where matter e ffects could be observed as a function of the baseline. We discuss the scal ing of rates, significances and sensitivities with the relevant mixing angl es and experimental parameters. Our analysis includes fluxes, event rates a nd statistical aspects so that the conclusions should be useful for the pla nning of experimental setups. We discuss the subleading amir effects in the case of the Delta M-21(2) MSW solution of the solar problem, showing that they are small for L greater than or similar to 7000 km. For shorter baseli nes, Delta m(21)(2) effects can be relevant and their dependence on L offer s a further handle for the determination of the CP-violation phase delta. F inally we comment on the possibility to measure the specific distortion of the energy spectrum due to the MSW effect. (C) 2000 Elsevier Science B.V. A ll rights reserved.