void treeviewer() {
//=========Macro generated by ROOT version3.00/00
//=========for tree "copac" (Fri Mar 23 10:00:42 2001)
//===This macro can be opened from a TreeViewer session after loading
//===the corresponding tree, or by running root with the macro name argument

   open_session();
}

open_session(void *p = 0) {
   gSystem->Load("libTreeViewer");
   TTreeViewer *treeview = (TTreeViewer *) p;
   if (!treeview) treeview = new TTreeViewer();
   TTree *tv_tree = (TTree*)gROOT->FindObject("copac");
   TFile *tv_file = (TFile*)gROOT->GetListOfFiles()->FindObject("hijing1.root");
   if (!tv_tree) {
      if (!tv_file) tv_file = new TFile("hijing1.root");
      if (tv_file)  tv_tree = (TTree*)tv_file->Get("copac");
      if(!tv_tree) {
         printf("Tree %s not found", fTree->GetName());
         return;
      }
   }

   treeview->SetTreeName("copac");
   treeview->SetNexpressions(10);
//         Set expressions on axis and cut
   TTVLVEntry *item;
//   X expression
   item = treeview->ExpressionItem(0);
   item->SetExpression("-log(tan(0.5*acos(fTracks.fPz/sqrt(fTracks.fPx*fTracks.fPx+fTracks.fPy*fTracks.fPy+fTracks.fPz*fTracks.fPz))))", "~eta");
//   Y expression
   item = treeview->ExpressionItem(1);
   item->SetExpression("", "-empty-");
//   Z expression
   item = treeview->ExpressionItem(2);
   item->SetExpression("", "-empty-");
//   Cut expression
   item = treeview->ExpressionItem(3);
   item->SetExpression("fTracks.fId==2112", "~neutroni");
//         Scan list
   item = treeview->ExpressionItem(4);
   item->SetExpression("", "Scan box");
//         User defined expressions
   item = treeview->ExpressionItem(5);
   item->SetExpression("-log(tan(0.5*acos(fTracks.fPz/sqrt(fTracks.fPx*fTracks.fPx+fTracks.fPy*fTracks.fPy+fTracks.fPz*fTracks.fPz))))", "~eta", kFALSE);
   item = treeview->ExpressionItem(6);
   item->SetExpression("fTracks.fId==2212", "~proton", kTRUE);
   item = treeview->ExpressionItem(7);
   item->SetExpression("0.5*log((fTracks.fE+fTracks.fPz)/(fTracks.fE-fTracks.fPz))", "~rap", kFALSE);
   item = treeview->ExpressionItem(8);
   item->SetExpression("fTracks.fId==2112", "~neutroni", kTRUE);
   item = treeview->ExpressionItem(9);
   item->SetExpression("", "-empty-", kFALSE);
   item = treeview->ExpressionItem(10);
   item->SetExpression("", "-empty-", kFALSE);
   item = treeview->ExpressionItem(11);
   item->SetExpression("", "-empty-", kFALSE);
   item = treeview->ExpressionItem(12);
   item->SetExpression("", "-empty-", kFALSE);
   item = treeview->ExpressionItem(13);
   item->SetExpression("", "-empty-", kFALSE);
   item = treeview->ExpressionItem(14);
   item->SetExpression("", "-empty-", kFALSE);
//--- session object
   tv_session = new TTVSession(treeview);
   treeview->SetSession(tv_session);
//--- tree viewer record
   tv_record = tv_session->AddRecord(kTRUE);
   tv_session->SetRecordName("rapiditate protoni");
   tv_record->fX        = "0.5*log((fTracks.fE+fTracks.fPz)/(fTracks.fE-fTracks.fPz))";
   tv_record->fY        = "";
   tv_record->fZ        = "";
   tv_record->fCut      = "fTracks.fId==2212";
   tv_record->fXAlias   = "~rap";
   tv_record->fYAlias   = "-empty-";
   tv_record->fZAlias   = "-empty-";
   tv_record->fCutAlias = "~proton";
   tv_record->fOption   = "";
   tv_record->fScanRedirected = kFALSE;
   tv_record->fCutEnabled = kTRUE;
//--- tree viewer record
   tv_record = tv_session->AddRecord(kTRUE);
   tv_session->SetRecordName("rapiditate neutroni");
   tv_record->fX        = "0.5*log((fTracks.fE+fTracks.fPz)/(fTracks.fE-fTracks.fPz))";
   tv_record->fY        = "";
   tv_record->fZ        = "";
   tv_record->fCut      = "fTracks.fId==2112";
   tv_record->fXAlias   = "~rap";
   tv_record->fYAlias   = "-empty-";
   tv_record->fZAlias   = "-empty-";
   tv_record->fCutAlias = "~neutroni";
   tv_record->fOption   = "";
   tv_record->fScanRedirected = kFALSE;
   tv_record->fCutEnabled = kTRUE;
//--- tree viewer record
   tv_record = tv_session->AddRecord(kTRUE);
   tv_session->SetRecordName("pseudorapiditate neutroni");
   tv_record->fX        = "-log(tan(0.5*acos(fTracks.fPz/sqrt(fTracks.fPx*fTracks.fPx+fTracks.fPy*fTracks.fPy+fTracks.fPz*fTracks.fPz))))";
   tv_record->fY        = "";
   tv_record->fZ        = "";
   tv_record->fCut      = "fTracks.fId==2112";
   tv_record->fXAlias   = "~eta";
   tv_record->fYAlias   = "-empty-";
   tv_record->fZAlias   = "-empty-";
   tv_record->fCutAlias = "~neutroni";
   tv_record->fOption   = "";
   tv_record->fScanRedirected = kFALSE;
   tv_record->fCutEnabled = kTRUE;
//--- Show first record
   tv_session->Show(tv_session->First());
}