Illustration of the parametric-space of the photon isolation momentum and the shower width parameter (\shshlo), used to estimate the background yield in the signal region ($\mathbb{A}$) from the observed yields in the three control regions ($\mathbb{B}$, $\mathbb{C}$, $\mathbb{D}$). The red regions indicate areas dominated by background and the blue regions those that contain the photon signal. The colour gradient between these regions illustrates the presence of a signal contribution in the three background zones.