Synthetic flat ntuples in the ROOT data format

These two datasets contain flat ntuples in the ROOT data format, synthetically produced using a ROOT macro. ROOT is the typical data format for storing High Energy Physics (HEP) data. In the ROOT context, a flat ntuple stores data not in the form of C++ object but each branch contains simple numbers (e.g. floating point numbers, integers) or vectors whose dimension might vary on an event-by-event basis. The two datasets have similar content and we distinguish them by adding the suffix <em>bkg</em> and <em>sgn</em> which stands for background and signal. There is no specific physics meaning behind these data. The two datasets contain both 5M of events and 50 branches, of which 10 contain integers, 10 floating point numbers, 10 vectors of integers, and 20 vectors of floating point numbers. The distributions used to fill the datasets are: gaussian, uniform, and exponential. The two datasets differ only on the content of two branches filled with vectors of floating point numbers, where a different mean and standard deviation have been set. These datasets have been produced to test the performance of the MLaaS4HEP framework. More info on the MLaaS4HEP framework in https://doi.org/10.1007/s41781-021-00061-3