Neutrino Oscillation Experiments for Precise Measurements of Oscillation Parameters and Search for numu->nue Appearance and CP Violation

The possibility of making a low cost, very intense high energy proton source at the Brookhaven Alternating Gradient Synchrotron (AGS) along with the forthcoming new large underground detectors at either the National Underground Science Laboratory (NUSL) in Homestake, South Dakota or at the Waste Isolation Pilot Plant (WIPP) in Carlsbad, New Mexico, allows us to propose a program of experiments that will address fundamental aspects of neutrino oscillations and CP-invariance violation. This program of experiments is unique because of the extra-long baseline of more than 2500 km from Brookhaven National Laboratory to the underground laboratories in the West, the high intensity of the proposed conventional neutrino beam, and the possibility of constructing a very large array of water Cerenkov detectors with total mass approaching 1 Megaton. As part of this program we also consider experiments at moderately long baselines (~400 km) using other detector technologies that can yield valuable and complementary information on neutrino oscillations. This letter of intent focuses on the design and construction of the necessary AGS upgrades and the new neutrino beam which will initially have a proton beam of power ~0.5 MW; the power will then be upgraded to ~1.3 MW in a later phase.