How to make a comparison using MC information: 0. Build the MC info tree gSystem->Load("libANALYSIS.so"); gSystem->Load("libPWG1.so") AliGenInfoMaker *t = new AliGenInfoMaker("galice.root","genTracks.root",0,0) t->Exec(); 1. Build the reconstructed info tree gSystem->Load("libANALYSIS.so"); gSystem->Load("libPWG1.so"); // AliRecInfoMaker *t2 = new AliRecInfoMaker("genTracks.root","cmpESDTracks.root","galice.root",0,0); t2->Exec(); 2. Make a chain of the information tree gSystem->Load("libANALYSIS.so"); gSystem->Load("libPWG1.so"); //GSI example .x ~/rootlogon.C gSystem->AddIncludePath("-I$ALICE_ROOT/TPC/macros") gROOT->LoadMacro("$ALICE_ROOT/TPC/macros/AliXRDPROOFtoolkit.cxx+") AliXRDPROOFtoolkit tool; TChain * chain = tool.MakeChain("cmp.txt","ESDcmpTracks",0,1000) chain->Lookup(); .L $ALICE_ROOT/PWG1/AliComparisonSelector.cxx+ 3. a.) Use AliTreeDraw for fast prototyping the queries - analysis type: gSystem->Load("libPWG1.so"); AliTreeDraw comp; comp.SetTree(tree) b.) Or use Selector chain->Process("$ALICE_ROOT/PWG1/AliComparisonSelector.cxx+") TFile f("Output.root");