  The paper discusses new method for electron/pion and muon/pion separation in
the Belle II detector at transverse momenta below 0.7 $\mathrm{GeV}/c$, which
is essential for efficient measurements of semi-leptonic decays of $B$ mesons
with tau lepton in the final state. The method is based on the analysis of
patterns in the electromagnetic calorimeter by using a Convolutional Neural
Network (CNN).
