Ntuples vs. TTreesIt is important to note the difference between the ROOT ntuple and the full ROOT Trees. Gleam actually provides 5 outputs: 1 summary ntuple file, and 4 full ROOT trees (Monte Carlo, Digitization, Reconstruction, and Relational Table). Ntuples. The summary ntuple and the full ROOT trees use the same basic format; however, the ntuple is simpler. As the name suggestion, the ntuple is tabular where each event consists of a fixed length row of data. Currently, each element in that row of data is a floating point value. In the near future, the ntuple structure will be updated to allow mixed data types, where each element could be an integer, float, double, or a fixed length array. Full ROOT Trees. Full ROOT trees are more complex, taking full advantage of ROOT's capability of storing C++ objects. The precise structure of the data pertaining to a specific event depends on the C++ class definition used to write to the ROOT Tree. More details on this will be provided in other sections of this workbook. Note: For an excellent introduction to C++, see Fermilab's ROOT Educational Resources page and refer to C++ Basics for ROOT users.
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