added EPOS4 generator for pp collisions at 13 TeV (#2082)

* added EPOS4 generator for pp collisions at 13 TeV

* added validation routine

Author: alcaliva

MC/config/examples/epos4/generator/pp_13TeV_hydro_cascade.optns

@@ -0,0 +1,32 @@
+!--------------------------------------------------------------------
+!           proton-proton collisions at 13 TeV with hydro and hadronic cascade
+!--------------------------------------------------------------------
+
+!---------------------------------------
+!            Define run
+!---------------------------------------
+
+application hadron !hadron-hadron, hadron-nucleus, or nucleus-nucleus
+set laproj 1 !projectile atomic number
+set maproj 1 !projectile mass number
+set latarg 1 !target atomic number
+set matarg 1 !target mass number
+set ecms 13000 !sqrt(s)_pp
+set istmax 25 !max status considered for storage
+
+ftime on     !string formation time non-zero
+!suppressed decays:
+nodecays
+ 110 20 2130 -2130 2230 -2230 1130 -1130 1330 -1330 2330 -2330 3331 -3331
+end
+
+set ninicon 1            !number of initial conditions used for hydro evolution
+core full                !core/corona activated
+hydro hlle               !hydro activated
+eos x3ff                 !eos activated (epos standard EoS)
+hacas full               !hadronic cascade activated (UrQMD)
+set nfreeze 1            !number of freeze out events per hydro event
+set modsho 1             !printout every modsho events
+set centrality 0         !0=min bias
+set ihepmc 2             !HepMC output enabled on stdout
+set nfull 10

MC/config/examples/ini/GeneratorEPOS4_pp13TeV.ini

@@ -0,0 +1,11 @@
+[GeneratorExternal]
+fileName=${O2DPG_MC_CONFIG_ROOT}/MC/config/examples/epos4/generator_EPOS4.C
+funcName=generateEPOS4("${O2DPG_MC_CONFIG_ROOT}/MC/config/examples/epos4/generator/pp_13TeV_hydro_cascade.optns", 2147483647)
+
+[GeneratorFileOrCmd]
+cmd=${O2DPG_MC_CONFIG_ROOT}/MC/config/examples/epos4/epos.sh
+bMaxSwitch=none
+
+# Set to version 2 if EPOS4.0.0 is used
+[HepMC]
+version=3

MC/config/examples/ini/tests/GeneratorEPOS4_pp13TeV.C

@@ -0,0 +1,64 @@
+int External()
+{
+  std::string path{"o2sim_Kine.root"};
+  // Check that file exists, can be opened and has the correct tree
+  TFile file(path.c_str(), "READ");
+  if (file.IsZombie())
+  {
+    std::cerr << "Cannot open ROOT file " << path << "\n";
+    return 1;
+  }
+  auto tree = (TTree *)file.Get("o2sim");
+  if (!tree)
+  {
+    std::cerr << "Cannot find tree o2sim in file " << path << "\n";
+    return 1;
+  }
+  std::vector<o2::MCTrack> *tracks{};
+  tree->SetBranchAddress("MCTrack", &tracks);
+
+  // Check if all events are filled
+  auto nEvents = tree->GetEntries();  
+  for (Long64_t i = 0; i < nEvents; ++i)
+  {
+    tree->GetEntry(i);
+    if (tracks->empty())
+    {
+      std::cerr << "Empty entry found at event " << i << "\n";
+      return 1;
+    }
+  }
+  // Check if there are 100 events, as simulated in the o2dpg-test
+  if (nEvents != 100)
+  {
+    std::cerr << "Expected 100 events, got " << nEvents << "\n";
+    return 1;
+  }
+  // check if each event has two protons with 6500 GeV of energy
+  // exits if the particle is not a proton
+  for (int i = 0; i < nEvents; i++)
+  {
+    auto check = tree->GetEntry(i);
+    int count = 0;
+    for (int idxMCTrack = 0; idxMCTrack < tracks->size(); ++idxMCTrack)
+    {
+      auto track = tracks->at(idxMCTrack);
+      double energy = track.GetEnergy();
+      // Check if track energy is approximately equal to 6500 GeV (a tolerance of 65 keV is considered, straight equality does not work due to floating point precision)
+      if (std::abs(energy - 6500) < 1e-4)
+      {
+        if (track.GetPdgCode() != 2212){
+          std::cerr << "Found 6500 GeV particle with pdgID " << track.GetPdgCode() << "\n";
+          return 1;
+        }         
+        count++;  
+      }
+    }
+    if (count < 2)
+    {
+      std::cerr << "Event " << i << " has less than 2 protons at 6500 GeV\n";
+      return 1;
+    }
+  }
+  return 0;
+}