Dark photon ntuple production (supersedes !346)

Production of ntuples, including MC, for \pi^0/\eta \rightarrow (A^\prime \rightarrow e^+ e^-) \gamma Run 2 analysis.

Instructions

When creating your merge request:

• Add a label for your WG
• Mark as "WIP:" until you're happy with the CI results
• If the merge request supersedes a previous one, add a comment at the end of the header: (supersedes !<MR number>). Please state explicitly in the description if the superseded ntuples can be deleted immediately, or after the new merge request is finalised

When ready:

• Remove the "WIP:" from the title:
• Assign the merge request to you working group's DPA/RTA liaison

To find your working group's DPA/RTA liaison, see this page:

https://twiki.cern.ch/twiki/bin/viewauth/LHCbPhysics/LHCbWGLiaisons