  Systematic analysis of the determination of the value of leptonic
CP-violating angle delta and the neutrino mass hierarchy sgn(delta m^2_31) by
long baseline neutrino oscillation experiments is presented. We note the
difficulty to distinguish a pair of oscillation probability spectra that are
peaked at the same energy and have the same probability at that energy. We
thereby set forth the peak-matching condition as a criterion of the presence of
degeneracy, and visualize it by intersections of the trajectories drawn by a
peak of an oscillation spectrum while the value of delta is varied from 0 to
2pi. We numerically calculate the pairs of the trajectories for both
hierarchies and show that the pair becomes disjoint as the baseline gets longer
than a critical length, indicating the matter effect resolving the degeneracy
on the hierarchy. We formulate the trajectories into analytic expressions and
evaluate the critical length. We provide prospects of the following four
approaches of resolving the hierarchy: making the baseline longer than the
critical length, using both neutrinos and anti-neutrinos, combining experiments
with different baseline lengths, and observing two or more oscillation peaks.
