Differences

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--- hepsim:jas4pp [2021/02/17 00:10]
hepsim17 [Jas4pp description]
+++ hepsim:jas4pp [2021/02/17 16:15]
hepsim17 [Reading ROOT files]
@@ Line 46: / Line 46: @@
   * 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 318: / 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 ======