Is there a tutorial on how to do the differential cross section’s histograms? (preferably with pyROOT, and I got my .root file using Delphes, and it looks like this:
I do not think this question is specific to ROOT. ROOT is a tool used by delphes to write xsction histos in a file, and is agnostic to their meaning or the conventions regulating their names.
My suggestion would be to look into Delphes documentation or the code that generated this file to find out.