parentsHist.py

import uproot
import awkward
import hist
import numpy as np
import os
import math

def get_root_parent(index, mcparticles):
         parents = mcparticles[index].member("parents").tolist()
         if len(parents) == 0:
                  return index
         elif len(parents) == 1:
                  return get_root_parent(parents.pop(), mcparticles)
         else:
                  raise Error("this cannot/should not happen")

if __name__ == '__main__':
         h1 = hist.Hist(hist.axis.Regular(bins=150, start=0, stop=45000, name="parent"))
         h2 = hist.Hist(hist.axis.Regular(bins=100, start=-70, stop=70, name="z"),
                        hist.axis.Regular(bins=100, start=0, stop=70, name="r"),
                        )
         x = uproot.open("C3SiD_300552.root")
         mcParticles = x["EVENT"]["MCParticles"].array(library="np")
         siVertexBarrelHits = x["EVENT"]["SiVertexBarrelHits"].array(library="np")

         for index in range(len(mcParticles[0])):
                  parent = get_root_parent(index, mcParticles[0])
                  h1.fill(parent=parent)

         for i in siVertexBarrelHits[0]:
                  x = i.member("position").member("fCoordinates").member("fX")
                  y = i.member("position").member("fCoordinates").member("fY")
                  z = i.member("position").member("fCoordinates").member("fZ")
                  h2.fill(z=z, r=math.sqrt(x*x+y*y))

         with uproot.recreate("parentHist.root") as f:
                  f["h1"] = h1
                  f["h2"] = h2