Average number of $\pi^{0}$ decays selected by the on-line stream
and S/B as functions of the crystal $\eta$ index. The $\eta$ indexes
of the two seed crystals from both photons forming
each selected $\pi^{0} \rightarrow \gamma\gamma$ candidate are used. To avoid
double counting, each entry is therefore assigned a weight of 0.5.
On the left, the total Monte Carlo rate is normalized to
that obtained in data. The shaded bands correspond to
the statistical uncertainty due to the limited size of the MC sample.