Differences

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--- hepsim:jas4pp [2021/02/14 03:14]
hepsim17 [Reading ROOT files]
+++ hepsim:jas4pp [2021/02/17 16:15] (current)
hepsim17 [Reading ROOT files]
@@ Line 41: / Line 41: @@
   * Downloading and searching HepSim data
   * Processing ProMC files from HepSim
+  * Processing ROOT files created by the Delphes program for fast simulation
   * Running over SLCIO files with Geant4 simulated / reconstructed events.
   * Data analysis (jets, physics vectors, histogram packages)
-  * Visualisation of reconstructed events using Wired4 display
+  * Visualization of reconstructed events using Wired4 display
-You can find more details in [[https://atlaswww.hep.anl.gov/hepsim/description.php|HepSim manual]].
+You can find more details in [[https://atlaswww.hep.anl.gov/hepsim/doc/doku.php|HepSim manual]].
@@ Line 198: / Line 199: @@
 ======  Reading ROOT files ======
-Jas4pp natively reads ROOT files including files created using ROOT (versions 3, 4, 5 and 6 are supported).
+Jas4pp natively reads commonly used objects and data structures from [[https://root.cern/ | ROOT files]]  (versions 3, 4, 5 and 6).
-One can find some examples in the directory "examples/root".
+ROOT files can be loaded using the Jas4pp menu [File]-[Open data source]-[Root file] (*.root).
-Here is a Jython/Python example showing how to read a ROOT tree:
+In addition, one can work with ROOT files using Python/Jython or Groovy scripts.
+One can find some examples in the directory "examples/root".  Here is a Jython/Python example showing how to read a ROOT tree:
 <hidden Show example of a Python code here>
@@ Line 316: / Line 318: @@
 The script that call these browsers  can be put into Jython or Groovy files and executed as binary programs.
+To read ROOT files from Delphes simulations, use
+[[https://atlaswww.hep.anl.gov/asc/jas4pp/api/rootio/Delphes.html|Delphes class]] and its "get" methods,
+getFloat, getDouble, getInt, and getBool. But first, explore the Delphes ROOT file using the browser shown above.
+Here is an example that uses high-level classes to read transverse momentum (PT) and pseudorapidity (ETA) of Monte Carlo particles:
+<hidden Click here to show  a Python code to read Delphes files>
+<code python>
+from  hep.io.root import RootFileReader
+from rootio import *
+reader = RootFileReader("mg5_ttbar_Njet_001.root" )
+tree = reader.get("Delphes");
+maxevents=tree.getEntries()
+branches=tree.getBranches()
+print "Nr of events=",tree.getEntries()
+print "Nr of branches=",branches.size()
+print "Branches:"
+for l in xrange( branches.size()  ):
+   print "Branch=",l," name=",(branches.get(l)).getName()
+particles=tree.getBranch("Particle") # get  generator particles
+ptEvents=Delphes.getFloat(particles,"PT")   # get PT array
+etaEvents=Delphes.getFloat(particles,"Eta") # get ETA array
+from jhplot import *
+h1 = H1D("PT of particles",100, 0, 100)
+h2 = H1D("Eta of particles",100, -4, 4)
+for i in xrange(tree.getEntries()):
+       pt,eta=ptEvents[i],etaEvents[i]
+       for j in xrange(len(pt)):
+           h1.fill(pt[j])
+           h2.fill(eta[j])
+c=HPlot("pT",600,300,2,1)
+c.visible()
+c.setAutoRange()
+c.draw(h1)
+c.cd(2,1)
+c.setAutoRange()
+c.draw(h2)
+</code>
+</hidden>
+{{:hepsim:pt_eta_delphes.png?300|}}
+<note warning>Reading Delphes trees is an experimental feature. Under study </note>
 ====== Using GUI mode ======