Hi,
I stumbled on the same problem, you can check the post here
you may want to try:
for entry in tree_file.Delphes:
eta = entry.GetLeaf("Tower.Eta").GetValue()
phi = entry.GetLeaf("Tower.Phi").GetValue()
I think this should work.
If not, try to upgrade to root 6.22/06
.
I think your method eta = entry.Tower.Eta
also should work there, but I am not sure.
cheers