There are a number of detector effects/errors that could mimic a W signal as well. A number of them are listed below, but this is most likely an imcomplete list at the moment and will be updated when more are thought of.
1) Hot-Towers - Some more QA needs to be done.
2) Random Track + Tower Matching - Look at the spectrum as a function of z-vertex (see if you get increased signal/background as a function of z. Should not have EEMC veto cut in this study because it already has a strong z dependence).
3) Inefficient veto cuts from dead area of TPC/BEMC/EEMC
4) Possible beam backgrounds in BTOW/TPC caused inefficient veto cuts
5) No CMB crossing tracks leads to increased background because of inefficiency of veto cuts - Can study this in simulation by dropping any track that crossing the CMB
6) t0 EEMC problem will effect the EEMC veto
7) Because of the EEMC time summing window, events with a vertex too close/too far will not have the proper energy in the EEMC which will cause an innefficiency in the veto and lead to an increased background.
8) If BTOW DB gains are very far from the truth this will cause an increased/decreased background in the signal region (stuff gets pushed up into or pushed out of the signal region)
9) L2W/BTH3 trigger background