  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.
