Azimuth angle is arbitrary. Figure 2 illustrates how the number of data events is determined for the optimal bin. The effectiveness and accuracy of the optimization procedure relies on MC techniques to calculate the average neutrino effective area and angular resolution. This was indirectly checked by examining the distributions of the analysis variables. Background MC and experimental data are compared at several steps in the analysis chain.
Good agreement helps to establish confidence in the signal simulation.
This comparison is discussed next.