\ The parametric space of the cluster isolation momentum and the shower width parameter (\sigmalongPb) in data for $R=0.2$ and $14\pt16$ \GeVc, used to estimate the background yield in the signal class (\textcolor{blue}{$\mathbb{A}$})from the observed yields in the three control classes (\textcolor{red}{$\mathbb{B}$}, \textcolor{red}{$\mathbb{C}$}, and \textcolor{red}{$\mathbb{D}$}). The dashed boxes indicate the limits of each class, the lower signal \ptIsoCh selection is open.