Olivier,
Trees are designed to have the same number of entries in all the
branches.
If this is not the case, you will have plenty of problems during the
tree
analysis, or when copying trees, etc.
Root gives the possibility to add a new branch to an existing tree.
It is the user's responsability to make sure that he fills correctly
this branch to be in sync with the other branches.
I think that adding a branch to an existing Tree is a bad idea in
general.
You better create a new Tree with the new branch(es).
There is no penalty in Root if you have one or many Trees. You can
perfectly
read several Trees in parralel.
In your case, what is the meaning of the single entry in the new branch?
Do you want to synchronize it with the first event of the other branch
or with
the last event ?
Rene Brun