under the directory 'scan_rootphenix'

run:     ' root -l  .x scanpico.C '

which contains essentially
void scanpico (char* InFile = "../../samples_root_files/picodstobj_Muon_500GeV_pro86-0000336436-9001.root")
 {
 char rep = 'y';
// faire tourner par root -l scanpico.C\(\"picodst.root\"\) pas de blanc  
 cout << endl << "************ " << endl;
 cout  << " Fichier scanne "  <<   InFile  << endl;
TFile *f = new TFile(InFile);
f.ls();
 cout << " the following supposes that data are in a  chain named T " << endl ;
cout << "continue ? n=stop " ; cin >> rep ;  cout << endl << "the answer is " << rep << endl ;
 if(rep == 'n') goto fini;
T->Show(11);

TH1D *hmt = new TH1D("hmt","masse tous evts",100,0.,5.);
T->Draw("DiMuons.mass>>hmt");



and  should lead to


************
 Fichier scanne ../../samples_root_files/picodstobj_Muon_500GeV_pro86-0000336436-9001.root
Warning: wrong member access operator '.' scanpico.C:13:
TFile**         ../../samples_root_files/picodstobj_Muon_500GeV_pro86-0000336436-9001.root      titled by PHOOL
 TFile*         ../../samples_root_files/picodstobj_Muon_500GeV_pro86-0000336436-9001.root      titled by PHOOL
  KEY: TTree    T;1     titled by PHOOL
  KEY: TTree    T1;1    titled by PHOOL
 the following supposes that data are in a  chain named T
continue ? n=stop y

the answer is y
======> EVENT:11
 DST/DiMuonContainer = NULL
 fUniqueID       = 0
 fBits           = 50331648
 nDiMuons        = 1
 DiMuons         = 1
 DiMuons.fUniqueID = 0
 DiMuons.fBits   = 50331648
 DiMuons.mass    = 1.562323
 DiMuons.charge  = -2
 DiMuons.same_event = 1
 DiMuons.rapidity = 2.083046
 DiMuons.X0      = -1.501837
 DiMuons.Y0      = -1.544188
 DiMuons.Z0      = 28.723722
 DiMuons.Px      = 0.954106
 DiMuons.Py      = 2.106953
 DiMuons.Pz      = 11.031026
 DiMuons.phi_dca = -2.397259
 DiMuons.r_dca   = 3.504395
 DiMuons.z_dca   = 38.689430
 DiMuons.Evt_vtxchi2 = 2.124907
 DiMuons.Evt_vtxoor = 0.365552
 DiMuons.costhCS = 0.160660
 DiMuons.costhGJ = -0.154904
 DiMuons.costhHX = 0.335125
 DiMuons.phiCS   = 1.599895
 DiMuons.phiGJ   = 0.000000
 DiMuons.phiHX   = 56643370876928.000000
 DiMuons.Tr0_px  = 1.488535
 DiMuons.Tr0_py  = 1.226628
 DiMuons.Tr0_pz  = 7.309620
 DiMuons.Tr0_rapidity = 2.040950
 DiMuons.Tr0_trhits = -193
 DiMuons.Tr0_idhits = 1023
 DiMuons.Tr0_DG0 = 6.296522
 DiMuons.Tr0_DDG0 = 0.699136
 DiMuons.Tr0_DS3 = 7.210942
 DiMuons.Tr0_trchi2 = 1.213184
 DiMuons.Tr0_idchi2 = 1.115829
 DiMuons.Tr0_ntrhits = 14
 DiMuons.Tr0_nidhits = 10
 DiMuons.Tr0_lastgap = 4
 DiMuons.Tr0_xst1 = 29.364122
 DiMuons.Tr0_xst2 = 68.770294
 DiMuons.Tr0_xst3 = 0.000000
 DiMuons.Tr0_yst1 = 23.398365
 DiMuons.Tr0_yst2 = 50.503738
 DiMuons.Tr0_yst3 = 0.000000
 DiMuons.Tr0_idx = 184.020248
 DiMuons.Tr0_idy = 112.660881
 DiMuons.Tr0_st1px = 1.297138
 DiMuons.Tr0_st1py = 0.997547
 DiMuons.Tr0_st1pz = 6.203116
 DiMuons.Tr0_MUID1D = 0
 DiMuons.Tr0_MUID1S = 0
 DiMuons.Tr0_dca_z = 18.220522
 DiMuons.Tr0_dca_r = 0.148149
 DiMuons.Tr1_px  = -0.344009
 DiMuons.Tr1_py  = 1.212887
 DiMuons.Tr1_pz  = 3.602403
 DiMuons.Tr1_rapidity = 1.769058
 DiMuons.Tr1_trhits = -12305
 DiMuons.Tr1_idhits = 990
 DiMuons.Tr1_DG0 = 3.053296
 DiMuons.Tr1_DDG0 = 5.661747
 DiMuons.Tr1_DS3 = 10.150540
 DiMuons.Tr1_trchi2 = 5.463346
 DiMuons.Tr1_idchi2 = 0.933808
 DiMuons.Tr1_ntrhits = 13
 DiMuons.Tr1_nidhits = 8
 DiMuons.Tr1_lastgap = 4
 DiMuons.Tr1_xst1 = -14.377878
 DiMuons.Tr1_xst2 = -21.057283
 DiMuons.Tr1_xst3 = 0.000000
 DiMuons.Tr1_yst1 = 47.170757
 DiMuons.Tr1_yst2 = 104.645782
 DiMuons.Tr1_yst3 = 0.000000
 DiMuons.Tr1_idx = -21.410414
 DiMuons.Tr1_idy = 272.968964
 DiMuons.Tr1_st1px = -0.148557
 DiMuons.Tr1_st1py = 0.756429
 DiMuons.Tr1_st1pz = 2.242194
 DiMuons.Tr1_MUID1D = 0
 DiMuons.Tr1_MUID1S = 0
 DiMuons.Tr1_dca_z = 17.699335
 DiMuons.Tr1_dca_r = 2.047522
 Evt_bbcZ        = 28.579313
 Evt_Cent        = 50.000000
 rx_S            = -999.000000
 rx_N            = -999.000000
 rx_NS           = -999.000000
 rx_Ninner       = -999.000000
 rx_Nouter       = -999.000000
 rx_Sinner       = -999.000000
 rx_Souter       = -999.000000
 DST/Sync        = NULL
 fUniqueID       = 0
 fBits           = 50331648
 eventcounter    = 293648
 eventnumber     = 18589678
 runnumber       = 336436
 segmentnumber   = 64
 DST/TrigLvl1    = NULL
 fUniqueID       = 0
 fBits           = 50331648
 lvl1_trigraw    = 53291
 lvl1_triglive   = 53291
 lvl1_trigscaled = 4096
 lvl1_clock_cross = 76
 lvl1_rbits[5]   = 1610614784 , 659653601 , 33554432 , 2349338626 , 352

 beamclk[2]      = 3284330208 , 15430

and a mass plot