Hi,
You can also use RVec in the JITted C++ (see the example in the documentation), I think Track_pt > 700. && Track_pt < X constructs an RVec<bool> that you can use to index any other Track_XYZ (for how to scale to a large number of branches the discussion Is there better way to filter array branches than defining new columns in RDataFrame? is a nice overview of the possibilities and limitations).
Cheers,
Pieter