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Agarwalla, S. K., Li, T., & Rubbia, A. (2012). An incremental approach to unravel the neutrino mass hierarchy and CP violation with a long-baseline superbeam for large theta(13). J. High Energy Phys., 05(5), 154–32pp.
Abstract: Recent data from long-baseline neutrino oscillation experiments have provided new information on theta(13), hinting that 0.01 less than or similar to sin(2) 2 theta(13) less than or similar to 0.1 at 2 sigma confidence level. In the near future, further confirmation of this result with high significance will have a crucial impact on the optimization of the future long-baseline neutrino oscillation experiments designed to probe the neutrino mass ordering and leptonic CP violation. In this context, we expound in detail the physics reach of an experimental setup where neutrinos produced in a conventional wide-band beam facility at CERN are observed in a proposed Giant Liquid Argon detector at the Pyhasalmi mine, at a distance of 2290 km. Due to the strong matter effects and the high detection efficiency at both the first and second oscillation maxima, this particular setup would have unprecedented sensitivity to the neutrino mass ordering and leptonic CP violation in the light of the emerging hints of large theta(13). With a 10 to 20 kt 'pilot' detector and just a few years of neutrino beam running, the neutrino mass hierarchy could be determined, irrespective of the true values of delta(CP) and the mass hierarchy, at 3 sigma (5 sigma) confidence level if sin(2) 2 theta(13)(true) = 0.05 (0.1). With the same exposure, we start to have 3 sigma sensitivity to CP violation if sin(2) 2 theta(13)(true) > 0.05, in particular testing maximally CP-violating scenarios at a high confidence level. After optimizing the neutrino and anti-neutrino running fractions, we study the performance of the setup as a function of the exposure, identifying three milestones to have roughly 30%, 50% and 70% coverage in delta(CP) (true) for 3 sigma CP violation discovery. For comparison, we also study the CERN to Slanic baseline of 1540 km. This work nicely demonstrates that an incremental program, staged in terms of the exposure, can achieve the desired physics goals within a realistically feasible timescale, and produce significant new results at each stage.
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Fernandez-Martinez, E., Li, T., Pascoli, S., & Mena, O. (2010). Improvement of the low energy neutrino factory. Phys. Rev. D, 81(7), 073010–13pp.
Abstract: The low energy neutrino factory has been proposed as a very sensitive setup for future searches for CP violation and matter effects. Here we study how its performance is affected when the experimental specifications of the setup are varied. Most notably, we have considered the addition of the “platinum'' nu(mu) -> nu(e) channel. We find that, while theoretically the extra channel provides very useful complementary information and helps to lift degeneracies, its practical usefulness is lost when considering realistic background levels. Conversely, an increase in statistics in the ”golden'' nu(mu) -> nu(e) channel and, to some extent, an improvement in the energy resolution, lead to an important increase in the performance of the facility, given the rich energy dependence of the "golden'' channel at these energies. We show that a low energy neutrino factory with a baseline of 1300 km, muon energy of 4.5 GeV, and either a 20 kton totally active scintillating detector or 100 kton liquid argon detector, can have outstanding sensitivity to the neutrino oscillation parameters theta(13), delta, and the mass hierarchy. For our estimated exposure of 2: 8 x 10(23) kton x decays per muon polarity, the low energy neutrino factory has sensitivity to theta(13) and delta for sin(2)(2 theta(13)) > 10(-4) and to the mass hierarchy for sin(2)(2 theta(13)) > 10(-3)
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