File Format

The input file format for SBNfit used to construct covariance matrices and central value predictions was decided during the 2017 Columbia workshop to be as simple and straightforward as possible in order to ensure that it could be used in all generic situations.

Input files are simple root files containing one or more TTrees that each analyzer constructs post-analysis from reconstructed variables that they wish to fit in.

The only two compulsory requirements in the input TTree are:

• A branch called weights that is a std::map<std::string, std::vector>
• A branch corresponding to whichever reconstructed variable the final fit and covariance matrix is to be build with, currently required to be a double

The weights branch is the standard EventWeight class format in which the string corresponds to the variation name (must be unique) and the vector corresponds to each individual weight for each universe. Note that each vector must be of identical size across different files for the same variation (string) but can change between different variations.

Some examples of such a simple file can be found at /uboone/data/users/markross/SBNfit_example_data/1e1p.root which contains a single tree (events) with the weights branch and a reconstructed energy variable ereco.

Multiple such files (or multiple TTrees in a single file), each corresponding to a different sample or background that one wishes to treat independently, are then used together in SBNfit to construct the covariance matrix. See Constructing a covariance matrix. There are multiple example files as used in the examples at /uboone/data/users/markross/SBNfit_example_data

If one wishes to do neutrino oscillations then in addition to the above two branches the file (or associated friend tree) must also contain

• A branch corresponding to true neutrino energy
• A branch corresponding to true neutrino oscillation length