New macro for impact parameter determination in pp events using reconstructed tracks

diff --git a/ITS/AliITSImpactParametersPP.C b/ITS/AliITSImpactParametersPP.C
new file mode 100644 (file)
index 0000000..f05c54b
--- /dev/null
+++ b/ITS/AliITSImpactParametersPP.C
@@ -0,0 +1,191 @@
+/****************************************************************************
+ *                                                                          *
+ * This macro determines the impact parameter of each track in pp event     *
+ * with respect to the primaty vertex position reconstructed using all      *
+ * the other tracks in the event. This procedure is necessary to avoid      *
+ * biases in the impact parameter estimate.                                 *
+ *                                                                          *
+ * Output:  TNtuple (ntd0) on file ImpactParameters.root                    *
+ *          There is one entry per track. The elements of the ntuple are:   *
+ *          1) Event: Event number                                          *
+ *          2) nTraks: Number of tracks for this event                      *
+ *          3) pt: Transverse momentum for the current track                *
+ *          4) d0rphi: transverse impact parameter of the current track     *
+ *          5) vx:     x coordinate of the vertex                           *
+ *          6) vy:     y coordinate of the vertex                           *
+ * origin: A.Dainese    andrea.dainese@pd.infn.it                           * 
+ ****************************************************************************/ 
+#if !defined(__CINT__) || defined(__MAKECINT__)
+//-- --- standard headers------------- 
+#include <Riostream.h>
+//--------Root headers ---------------
+#include <TSystem.h>
+#include <TFile.h>
+#include <TNtuple.h>
+#include <TString.h>
+#include <TStopwatch.h>
+#include <TObject.h>
+#include <TVector3.h>
+#include <TTree.h>
+#include <TParticle.h>
+#include <TArray.h>
+//----- AliRoot headers ---------------
+#include "alles.h"
+#include "AliRun.h"
+#include "AliKalmanTrack.h"
+#include "AliITStrackV2.h"
+#include "AliHeader.h"
+#include "AliGenEventHeader.h"
+#include "AliV0vertex.h"
+#include "AliV0vertexer.h"
+#include "AliITSVertex.h"
+#include "AliITSVertexer.h"
+#include "AliITSVertexerTracks.h"
+#endif
+//-------------------------------------
+
+// field (T)
+const Double_t kBz = 0.4;
+
+// this function ckecks file existence
+Bool_t GetInputFile();
+void   MoveTracks(TTree& itsTree,TObjArray& array);
+
+
+void   AliITSImpactParametersPP(Int_t evFirst=0,Int_t evLast=0) {
+
+  const Char_t *name="AliITSImpactParametersPP";
+  cerr<<'\n'<<name<<"...\n";
+  gBenchmark->Start(name);  
+
+  AliKalmanTrack::SetConvConst(100/0.299792458/kBz);
+
+
+  // check existence of input file
+  if(!GetInputFile()) { cerr<<"No tracks file found"<<endl; return; }
+
+  TString outName("ImpactParameters.root");
+
+  // primary vertex
+  Double_t v1[3] = {0.,0.,0,};
+  
+  Int_t    ev,itsEntries,i;
+  Int_t    nTotEv=0;
+  Double_t pt,d0rphi;
+  Char_t   trksName[100];
+  AliITStrackV2 *itstrack = 0;
+
+  // output ntuple
+  TNtuple *ntd0 = new TNtuple("ntd0","ntd0","Event:nTrks:pt:d0rphi:vx:vy");
+
+  // create the AliITSVertexerTracks object
+  AliITSVertexerTracks *vertexer1 = new AliITSVertexerTracks;
+  vertexer1->SetMinTracks(3);
+  vertexer1->SetDebug(0);
+  Int_t skipped[2];
+
+  // Open file with ITS tracks
+  TFile* itstrks = TFile::Open("AliITStracksV2.root");
+
+
+  // loop on events in file
+  for(ev=evFirst; ev<=evLast; ev++) {
+    printf(" --- Processing event  %d ---\n",ev);
+    sprintf(trksName,"TreeT_ITS_%d",ev);
+
+    // tracks from ITS
+    TTree *itsTree  =(TTree*)itstrks->Get(trksName);
+    if(!itsTree) continue;
+    itsEntries = (Int_t)itsTree->GetEntries();
+    printf("+++\n+++ Number of tracks in ITS: %d\n+++\n\n",itsEntries);
+
+    TObjArray tArray(itsEntries);
+    MoveTracks(*itsTree,tArray);
+    
+    // count the total number of events
+    nTotEv++;
+
+    // loop on tracks
+    for(i=0; i<itsEntries; i++) {
+      itstrack = (AliITStrackV2*)tArray.At(i);
+
+      // pt
+      pt = 1./TMath::Abs(itstrack->Get1Pt());
+
+      // primary vertex from other tracks in event
+      Bool_t goodVtx = kFALSE;
+      vertexer1->SetVtxStart(0.,0.);
+      skipped[0] = i;
+      skipped[1] = -1;
+      vertexer1->SetSkipTracks(1,skipped);
+      AliITSVertex *vertex1 = 
+        (AliITSVertex*)vertexer1->VertexOnTheFly(*itsTree); 
+      if(vertex1->GetNContributors()>0) goodVtx = kTRUE; 
+      vertex1->GetXYZ(v1);
+      //vertex1->PrintStatus(); 
+      // impact parameter w.r.t. v1      (in microns)
+      d0rphi =  10000.*itstrack->GetD(v1[0],v1[1]);
+      delete vertex1;
+
+      // fill ntuple
+      if (goodVtx) ntd0->Fill(ev,itsEntries,pt,d0rphi,v1[0],v1[1]);
+
+      itstrack = 0;
+    }   // loop on tracks
+
+    delete itsTree;
+
+  }    // loop on events in file
+
+
+  printf("\n+++\n+++ Total number of events: %d\n+++\n",nTotEv);
+
+  delete vertexer1;
+
+  itstrks->Close();
+
+  // store ntuple in a file
+  TFile* outroot = new TFile(outName.Data(),"recreate");
+  ntd0->Write();
+  outroot->Close();
+  delete outroot;
+
+
+  gBenchmark->Stop(name);
+  gBenchmark->Show(name);
+
+  return;
+}
+//___________________________________________________________________________
+Bool_t   GetInputFile() {
+  TString itsName("AliITStracksV2.root");
+
+  if(gSystem->AccessPathName(itsName.Data(),kFileExists)) return kFALSE;
+
+  return kTRUE;
+}
+//___________________________________________________________________________
+void MoveTracks(TTree& itsTree,TObjArray& array) {
+//
+// this function creates two TObjArrays with tracks
+//
+ 
+  Int_t entr = (Int_t)itsTree.GetEntries();
+
+  // trasfer tracks from tree to array
+  for(Int_t i=0; i<entr; i++) {
+
+    AliITStrackV2 *t = new AliITStrackV2; 
+    itsTree.SetBranchAddress("tracks",&t);
+
+    itsTree.GetEvent(i);
+
+    array.AddLast(t);
+
+  }
+
+  return;
+}
+
+
+