Add configuration for Pb-Pb with hadronic rescattering (#2364)

* Add configuration for Pb-Pb with hadronic rescattering

* Update PbPb Angantyr settings

Author: romainschotter

MC/config/common/ini/pythia8_PbPb_rescattering_536.ini

@@ -0,0 +1,10 @@
+#NEV_TEST> 1
+[Diamond]
+width[2]=6.0
+
+[GeneratorExternal]
+fileName=${O2DPG_MC_CONFIG_ROOT}/MC/config/ALICE3/pythia8/generator_pythia8_ALICE3.C
+funcName=generator_pythia8_ALICE3()
+
+[GeneratorPythia8]
+config=${O2DPG_MC_CONFIG_ROOT}/MC/config/common/pythia8/generator/pythia8_PbPb_rescattering_536.cfg

MC/config/common/ini/tests/pythia8_PbPb_rescattering_536.C

@@ -0,0 +1,24 @@
+int External() {
+  std::string path{"o2sim_Kine.root"};
+
+  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);
+
+  auto nEvents = tree->GetEntries();
+  if (nEvents == 0) {
+    std::cerr << "No event of interest\n";
+    return 1;
+  }
+  return 0;
+}

MC/config/common/pythia8/generator/pythia8_PbPb_rescattering_536.cfg

@@ -0,0 +1,24 @@
+### OO beams
+Beams:idA 1000822080		# Pb
+Beams:idB 1000822080		# Pb       
+Beams:eCM = 5360.0                ### energy
+    
+Beams:frameType = 1
+ParticleDecays:limitTau0 = on
+ParticleDecays:tau0Max = 10.      ### match alice: 1cm/c = 10.0mm/c
+
+### Initialize the Angantyr model to fit the total and semi-includive
+### cross sections in Pythia within some tolerance.
+HeavyIon:SigFitErr = 0.02,0.02,0.1,0.05,0.05,0.0,0.1,0.0
+
+### These parameters are typicall suitable for sqrt(S_NN)=5TeV
+HeavyIon:SigFitDefPar = 17.24,2.15,0.33,0.0,0.0,0.0,0.0,0.0
+
+### enable hadronic rescattering
+HadronLevel:Rescatter = on # default = off
+Fragmentation:setVertices = on # default = off
+PartonVertex:setVertex = on # default = off
+Rescattering:nearestNeighbours = off # default = on (but "require a larger retuning effort")
+Rescattering:inelastic = on # default = on
+    
+Random:setSeed = on