Megaton Modular Multi-Purpose Neutrino Detector

This brief note outlines a detector for the Homestake Laboratory and the physics experiments that might be done with it. The note might go on record as a letter of intent to be converted to a formal proposal at a later time. A major challenge to be faced in the construction of a multipurpose underground laboratory lies in the design of the rooms required by the most massive detectors, their sizes, implementation, configuration, and depth. Smaller rooms present other, usually less serious problems. Accordingly, it is useful to address the physics that demands massive detectors at an early time so that the issues and expense involved in constructing them are appropriately delineated in the overall description of the laboratory. That is the purpose of this note. The characteristics of the Homestake Underground Laboratory, very deep laboratory chambers and very strong rock, open the possibility of a new generation of extremely large detectors that can explore hitherto unexamined domains of the Universe and of fundamental physics interactions. Among the recognized scientific goals of such a detector system are: a. Search for proton decays one or more orders of magnitude in lifetime beyond the present experimental limits b. Search for localized or diffuse astrophysical sources of ultra high energy (UHE) neutrinos. c. Extend the investigation of neutrino flavor transitions of atmospheric neutrinos beyond the range explored by Superkamiokande by significantly more statistics. d. Detect neutrino bursts from supernova and, especially, detect the neutrinos from the electron capture reaction at the formation of the protoneutron star. e. Provide a potential target for future very intense terrestrial sources of neutrinos with emphasis on a search for CP invariance violation in the neutrino sector. f. Permit additional high statistics investigations of solar neutrino emission, if that is still required. The large water Cerenkov detectors at Lake Erie, Sudbury and Kamioka, (Kamiokande II and Superkamiokande) have beautifully demonstrated the capability of such detectors to study neutrino emission by the Sun, to investigate the time of flight dependence of neutrino flavor transitions, to search for baryon number violation via the decay of the proton and to observe neutrinos from supernova. The largest of these detectors, Superkamiokande (SK), has a total water volume of 50, 000m and is at a depth of approximately 2700 mwe.