from the final analysis.[]{data-label="fig:sigmaMoverM"}](Figure_001-a.pdf "fig:"){width="45.00000%"} ![Comparison of the decorrelated mass resolution estimator [$\sigma_{m}^{D}$]{}distributions in data and simulation for [$\cPZ\to\Pep\Pem$]{}events where both electrons are reconstructed as photons, passing the selection defined in Section \[sec:selection\]. The impact of the systematic uncertainty in the $\sigma_E/E$ is indicated by the red band. The distributions are shown separately for events with both electrons in the EB (left) and the remainder of the events, , events with at least one photon in the EE (right). Events in the shaded gray region are discarded from the final analysis.[]{data-label="fig:sigmaMoverM"}](Figure_001-b.pdf "fig:"){width="45.00000%"}

Event categorization {#sec:categorization}
====================

Events with both photons passing a minimum requirement on the output of the photon identification classifier, are sorted into categories of [$\sigma_{m}^{D}$]{}to maximize the analysis sensitivity to the SM Higgs boson. The number of categories and the positions of their [$\sigma_{m}^{D}$]{}boundaries are optimized simultaneously with the lower bound on the output of the photon identification classifier. Three categories, labeled 0, 1, and 2 in ascending order of [$\sigma_{m}^{D}$]{}values, are found adequate to saturate the maximum sensitivity achievable with this method for the present data set. The boundaries of the [$\sigma_{m}^{D}$]{}categorization are found to be $0$, $0.0084$, $0.012$, $0.030$, with a minimum requirement on the 