Issue reported by Ricardo Vazquez Gomez.
The example uses S21 which was special in many senses. One of them, was that during the stripping a new reconstruction of the calorimeter was applied. This was the first (and last) time that such a thing was done as it created a lot of problems.
The bottomline is that if the new calo reconstruction is not applied when redoing the stripping, then data and MC don’t have the same reconstruction version and cannot be compared (the same effect as having Reco12 MC and Reco14 data). This affect not only photons and electrons, but also all of the PID-related variables for every particle species.
https://svnweb.cern.ch/trac/lhcb/browser/DBASE/trunk/AppConfig/options/DaVinci/DV-RedoCaloPID-Stripping21.py
and again, should only be used for S21.
gaudirun.py options.py DV-RedoCaloPID-Stripping21.py