Changes between Initial Version and Version 1 of WorkBook/Tutorials/Prefit

Timestamp:

Mar 5, 2020, 11:15:26 AM (5 years ago)

Author:

Michele Selvaggi

Comment:

--

WorkBook/Tutorials/Prefit

@@ +1 @@
+[[TOC]]
+
+= Delphes Tutorial - DESY March 2020 =
+
+== Pre-requisites ==
+
+To successfully run this tutorial the Delphes  virtual machine should be installed, see here for more information:
+
+https://twiki.cern.ch/twiki/bin/view/VBSCan/PREFIT20
+
+
+
+- gcc/tcl:
+
+For linux users gcc/tcl should be already installed. For Mac users you should install XCode.
+
+- ROOT:
+
+can be downloaded from https://root.cern.ch/downloading-root
+Go on latest release, and download a version under "Binary distributions".
+
+- Pythia8:
+
+following instructions from here (or using the Pythia8 installation in !MadGraph):
+
+https://cp3.irmp.ucl.ac.be/projects/delphes/wiki/WorkBook/Pythia8
+
+The solutions for all the exercises can be found in the attachment file (suggestion: download file locally). 
+
+== I) Event generation with Pythia8 + Delphes sample ==
+
+This exercise will teach how to configure the Pythia8 event generator for a simple production of e+e- -> ZH events. Next, you will generate events and simulate the detector with the DelphesPythia8 executable.
+
+1) Create a Pythia8 configuration card that generates N=10k events of ee->Zh->mumu at sqrt(s)=240 GeV (call it "examples/Pythia8/config_ee_zh_zmumu.cmd").
+
+{{{
+Main:numberOfEvents = 10000         ! number of events to generate
+
+Beams:idA = 11                   ! first beam, e- = -11
+Beams:idB = -11                  ! second beam, e+ = 11
+Beams:eCM = 240.                 ! CM energy of collision
+
+! Higgsstrahlung process
+HiggsSM:ffbar2HZ = on
+
+! 5) Force the Z decays to muons
+23:onMode = off
+23:onIfAny = 13 -13
+}}}
+
+2) Produce Delphes events using the above Pythia8 configuration (this command should run Pythia and Delphes on the fly!), using the CEPC detector card "cards/delphes_card_CEPC.tcl"
+
+{{{
+./DelphesPythia8 cards/delphes_card_CEPC.tcl examples/Pythia8/config_ee_zh_zmumu.cmd delphes_ee_zh_zmumu.root
+}}}
+
+== II) Simple Tree analysis ==
+
+
+1) Open Delphes ROOT tree and explore the branches
+
+{{{
+root -l delphes_ee_zh_zmumu.root
+gSystem->Load("libDelphes");
+TBrowser t;
+}}}
+
+
+Note: Most objects are described in terms of pp specific variables (PT, Eta, Phi).
+This is simply for historical reasons (and makes of course no difference whatsoever) since Delphes was developed originally as a tool for LHC physics. To plot ee-like variables, one needs to write the translation (or make use of the very useful TLorentzVector of ROOT, see part III).
+
+2) Interactively draw the muon multiplicity and the jet multiplicity. You first have to double-click on the root file icon in the TBrowser. Do you understand these distributions?
+
+{{{
+Delphes->Draw("Muon_size");
+Delphes->Draw("Jet_size");
+}}}
+
+== III) Write a simple analysis macro ==
+
+1) Write down the formula for the recoil Higgs mass.
+
+2) You can find a simple analysis macro in "example/Example1.py". It can be executed like this:
+
+{{{
+python examples/Example1.py delphes_ee_zh_zmumu.root out.root
+}}}
+
+This Example1.py macro does not produce anything interesting here (it most likely produce an empty plot). The above command is simply shown as an example for how to run a macro. You should open Example1.py with a text editor, and write a small analysis that first selects events with two muons and then reconstructs and plot the recoil Higgs mass using the formula found in III.1)
+
+
+Solution:
+
+{{{
+# Recoil Mass macro
+#!/usr/bin/env python
+
+import sys
+import ROOT
+
+if len(sys.argv) < 2:
+  print " Usage: python examples/MissingMass.py delphes_ee_zh_zmumu.root hist_mrec.root"
+  sys.exit(1)
+
+ROOT.gSystem.Load("libDelphes")
+
+try:
+  ROOT.gInterpreter.Declare('#include "classes/SortableObject.h"')
+  ROOT.gInterpreter.Declare('#include "classes/DelphesClasses.h"')
+  ROOT.gInterpreter.Declare('#include "external/ExRootAnalysis/ExRootTreeReader.h"')
+except:
+  pass
+
+inputFile = sys.argv[1]
+outputFile = sys.argv[2]
+
+# Create chain of root trees
+chain = ROOT.TChain("Delphes")
+chain.Add(inputFile)
+
+# Create object of class ExRootTreeReader
+treeReader = ROOT.ExRootTreeReader(chain)
+numberOfEntries = treeReader.GetEntries()
+
+# Get pointers to branches used in this analysis
+branchMuon = treeReader.UseBranch("Muon")
+
+# Book histograms
+histMass = ROOT.TH1F("mass", "M_{recoil} [GeV]", 60, 100.0, 160.0)
+
+ptot = ROOT.TLorentzVector(0.,0.,0.,240.)
+# Loop over all events
+for entry in range(0, numberOfEntries):
+  # Load selected branches with data from specified event
+  treeReader.ReadEntry(entry)
+
+  # If event contains at least 2 muons
+  if branchMuon.GetEntries() > 1:
+
+    mu1 = branchMuon.At(0)
+    mu2 = branchMuon.At(1)
+
+    pll = mu1.P4() + mu2.P4()
+    ph = ptot - pll
+
+    histMass.Fill(ph.M())
+
+out_root = ROOT.TFile(outputFile,"RECREATE")
+histMass.Write()
+}}}
+
+== IV) Modify the Delphes detector card ==
+
+
+You have now produced a Delphes simulated event with the hypothetical CEPC default detector configuration.
+
+1) Can you think of 2 detector parameters that determine and drive the sensitivity of the Higgs recoil measurement in this particular final state?
+
+2) Identify where they are configured in the delphes detector card.
+
+3) Create two new detector configurations by degrading these two parameters by a sizable factor.
+
+4) Reproduce a Delphes sample with these new configurations and observe the impact on the recoil mass distribution.
+