example of MC truth filtering using analysis_utils

mctruth.py

import sys
import ROOT as r
from analysis_utils.root.dpd_object import get_objects, build_tlv
 
if __name__ == "__main__":
 t = r.TChain("physics")
 map(t.Add, sys.argv[1:])
 
 for evt in t:
  # pull lightweight 'objects' from the mc_* branches
  truth_particles = get_objects(t, 'mc')
  
  # select only the electrons
  truth_electrons = [p for p in truth_particles if abs(p.pdgId)==11]
  
  # require status == 3
  final_electrons = [el for el in truth_electrons if el.status==3]
  
  # require truth pt > 7 GeV
  hard_electrons = [el for el in truth_electrons if el.pt > 7e3]
  
  # require 2 such electrons
  if not len(hard_electrons) >= 2: continue
 
  # build a TLorentzVector from the (pt,eta,phi,m) for all electrons
  map(build_tlv, hard_electrons)
  
  # grab the first two and print some info:
  el1, el2 = hard_electrons[:2]
  print 'el1 pt=%d, eta=%.2f, phi=%.2f' % (el1.pt, el1.eta, el1.phi)
  print 'el2 pt=%d, eta=%.2f, phi=%.2f' % (el2.pt, el2.eta, el2.phi)
  
  # add up the tlv's for the electrons and print the inv. mass
  electron_system = el1.tlv + el2.tlv
  print "Electron system mass: ", electron_system.M()