Exploring neutrino oscillations with superbeams - art. no. 113011

We consider the medium- and long-baseline oscillation physics capabilities of intense muon-neutrino and muon-antineutrino beams produced using future upgraded megawatt-scale high-energy proton beams. In particular we consider the potential of these conventional neutrino "superbeams" for observing nu (mu)-->nu (e) oscillations, determining the hierarchy of neutrino mass eig enstates, and measuring CP Violation in the lepton sector. The physics capa bilities of superbeams are explored as a function of the beam energy, basel ine, and the detector parameters (fiducial mass, background rarest and syst ematic uncertainties on the backgrounds). The trade-offs between very large detectors with poor background rejection and smaller detectors with excell ent background rejection are illustrated. We find that, with an aggressive set of detector parameters, it may be possible, to observe nu (mu)-->nu (e) oscillations with a superbeam provided that the amplitude parameter sin(2) 2 theta (13) is larger than a few x 10(-3). If sin(2)2 theta (13) is of ord er 10(-2) or larger, then the neutrino mass hierarchy can be determined in long-baseline experiments, and if in addition the large mixing angle MSW so lution describes the solar neutrino deficit, then there is a small region o f parameter space within which maximal CP violation in the lepton sector wo uld be observable (with a significance of a few standard deviations) in a l ow-energy medium-baseline experiment. We illustrate our results by explicit ly considering massive water Cherenkov and liquid argon detectors at superb eams with neutrino energies ranging from 1 GeV to 15 GeV, and baselines ran ging from 295 km to 9300 km. Finally, we compare the oscillation physics pr ospects at superbeams with the corresponding prospects at neutrino factorie s. The sensitivity at a neutrino factory to CP violation and the neutrino m ass hierarchy extends to values of the amplitude parameter sin(2)2 theta (1 3) that are one to two orders of magnitude lower than at a superbeam.