科研之友
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摘要
The three major unknown neutrino oscillation parameters at the present juncture are the mass hierarchy, the octant of the mixing angle theta(23) and the CP phase delta(CP). It is well known that the presence of hierarchy-delta(CP) and octant degeneracies affects the unambiguous determination of these parameters. In this paper, we show that a comprehensive way to study the remaining parameter degeneracies is in the form of a generalized hierarchy -theta(23) - delta(CP) degeneracy. This is best depicted as contours in the test (theta(23) - delta(CP)) plane for different representative true values of parameters. We show that the wrong-hierarchy and/or wrong-octant solutions can be further classified into eight different solutions depending on whether they occur with the wrong or right value of delta(CP). These eight solutions are different from the original eightfold degenerate solutions and can exist, in principle, even if theta(13) is known. These multiple solutions, apart from affecting the determination of the true hierarchy and octant, also affect the accurate estimation of delta(CP). We identify which of these eight different degenerate solutions can occur in the test (theta(23) - delta(CP)) parameter space, taking the long-baseline experiment NO nu A running in the neutrino mode as an example. The inclusion of the NO nu A antineutrino run removes the wrong-octant solutions appearing with both right and wrong hierarchy. Adding T2K data to this resolves the wrong hierarchy-right octant solutions to a large extent. The remaining wrong-hierarchy solutions can be removed by combining NO nu A + T2K with atmospheric neutrino data. We demonstrate this using ICAL@INO as the prototype atmospheric neutrino detector. We find that the degeneracies can be resolved at the 2 sigma level by the combined data set, for the true parameter space considered in the study.
- 出版日期2016-1-14
