Effect of non-zero theta(13) on the measurement of theta(23)

Abstract

The moderately large measured value of theta13 signals a departure from the approximate two-flavour oscillation framework. As a consequence, the relation between the value of theta23 in nature, and the mixing angle measured in muon neutrino disappearance experiments is non-trivial. In this paper, we calculate this relation analytically. We also derive the correct conversion between degenerate values of theta23 in the two octants. Through simulations of a muon neutrino disappearance experiment, we show that there are observable consequences of not using the correct relation in calculating oscillation probabilities. These include a wrong best-fit value for theta23, and spurious sensitivity to the octant of theta23.