Attempt to produce pyxsec.root file for Pythia8 runs, not successful yet

MC/sim.C

@@ -48,12 +48,20 @@ void sim()
 }
 
 WriteXsection()
+{
+  if (WriteXsection_Pythia6()) return;
+  if (WriteXsection_Pythia8()) return;
+}
+
+Bool_t
+WriteXsection_Pythia6()
 {
 
   TPythia6 *pythia = TPythia6::Instance();
-  if (!pythia) return;
+  if (!pythia) return kFALSE;
   pythia->Pystat(1);
   Double_t xsection = pythia->GetPARI(1);
+  if (xsection < 1.e-30) return kFALSE;
   UInt_t ntrials = pythia->GetMSTI(5);
   TFile *file = new TFile("pyxsec.root","recreate");
   TTree *tree = new TTree("Xsection","Pythia cross section");
@@ -62,7 +70,29 @@ WriteXsection()
   tree->Fill();
   tree->Write();
   file->Close();
-  cout << "Pythia cross section: " << xsection
+  cout << "Pythia6 cross section: " << xsection
        << ", number of trials: " << ntrials << endl;
+  return kTRUE;
+}
 
+Bool_t
+WriteXsection_Pythia8()
+{
+
+  AliPythia8 *pythia = AliPythia8::Instance();
+  if (!pythia) return kFALSE;
+  pythia->Pystat(1);
+  Double_t xsection = pythia->GetXSection();
+  if (xsection < 1.e-30) return kFALSE;
+  UInt_t ntrials = 0; // fix me please!
+  TFile *file = new TFile("pyxsec.root","recreate");
+  TTree *tree = new TTree("Xsection","Pythia cross section");
+  TBranch *branch = tree->Branch("xsection", &xsection, "X/D");
+  TBranch *branch = tree->Branch("ntrials" , &ntrials , "X/i");
+  tree->Fill();
+  tree->Write();
+  file->Close();
+  cout << "Pythia8 cross section: " << xsection
+       << ", number of trials: " << ntrials << endl;
+  return kTRUE;
 }