A cluster finder and hit reconstruction class for RICH (adapted from MUON).

[u/mrichter/AliRoot.git] / RALICE / AliInvmass.cxx

diff --git a/RALICE/AliInvmass.cxx b/RALICE/AliInvmass.cxx
index c782b8851779b46ef137af3cd9c31eeb561b0d20..a54c867e316d2f97fc335fe0d2bd5303521ac8ec 100644 (file)
--- a/RALICE/AliInvmass.cxx
+++ b/RALICE/AliInvmass.cxx
@@ -15,8 +15,97 @@
 
 /*
 $Log$
+Revision 1.2  1999/09/29 09:24:28  fca
+Introduction of the Copyright and cvs Log
+
 */
 
+////////////////////////////////////////////////////////////////////////////////
+// Class AliInvmass
+// Construction of invariant mass and combinatorial background.
+//
+// Example :
+// ---------
+//
+// TObjArray* photons=new TObjArray(); // Array with photon tracks for pi0 rec.
+//
+// // Code to create some photon tracks from pi0 decays
+// Int_t ntracks=200;
+// for (Int_t i=0; i<ntracks; i++)
+// {
+//  photons->Add(new Alitrack);
+//  ...
+//  ...
+//  ...
+// }  
+//
+// // Perform the invariant mass and comb. bkg. reconstruction
+//
+// TObjArray* allm=q.Invmass(photons,photons); // All reconstructed invariant masses
+//
+// TH1F* hall=new TH1F("hall","hall",200,0,2); // Histo with M_inv of all combinations
+//
+// Int_t nall=0;
+// if (allm) nall=allm->GetEntries();
+//
+// AliTrack* t;
+// Float_t minv;
+// for (Int_t j=0; j<nall; j++)
+// {
+//  t=(AliTrack*)allm->At(j);
+//  if (t)
+//  {
+//   minv=t->GetMass();
+//   hall->Fill(minv);
+//  }
+// }
+//
+// TObjArray* bkgm=q.CombBkg(photons,photons); // Reconstructed comb. background
+//
+// TH1F* hbkg=new TH1F("hbkg","hbkg",200,0,2); // Histo with M_inv. of comb. background
+//
+// Int_t nbkg=0;
+// if (bkgm) nbkg=bkgm->GetEntries();
+//
+// for (Int_t j=0; j<nbkg; j++)
+// {
+//  t=(AliTrack*)bkgm->At(j);
+//  if (t)
+//  {
+//   minv=t->GetMass();
+//   hbkg->Fill(minv);
+//  }
+// }
+//
+// TH1F* hsig=new TH1F("sig","sig",200,0,2);   // Histo with the bkg. subtracted signal
+// hsig->Sumw2();
+// hsig->Add(hall,hbkg,1,-1);
+//
+//
+// Note : By default the storage of the reconstructed information is performed
+//        in separate TObjArrays for the signal and comb. background resp.
+//        In order to limit the memory usage, AliInvmass::SetStorageMode(1) may be
+//        used to activate only a single TObjArray to store the reconstructed information.
+//        Consequently, the following statements 
+//
+//         TObjArray* allm=q.Invmass(photons,photons);
+//         TObjArray* bkgm=q.CombBkg(photons,photons);
+//
+//        will result in the fact that after he invokation of CombBkg
+//        the information of "allm" is lost due to the fact that the storage is
+//        is re-used for "bkgm" in case the "single storage" option has been selected.
+//        Usage of the, in that case invalid, pointer "allm" may cause your
+//        program to crash.
+//
+//        * Thus : In case of single storage usage, all invokations of the returned
+//                 array pointer have to be completed before invoking any memberfunction
+//                 of the same AliInvmass object again.
+//        
+//        
+//
+//--- Author: Nick van Eijndhoven 12-apr-1999 UU-SAP Utrecht
+////////////////////////////////////////////////////////////////////////////////
+
 #include "AliInvmass.h"
  
 ClassImp(AliInvmass) // Class implementation to enable ROOT I/O