I have a dst file but I can't read it

I hava a .dst file and there is a TTree in it. When I read the TTree and use the Print() method, it shows:

******************************************************************************
*Tree    :Event     : Event from conversion                                  *
*Entries :    50000 : Total =      1888162711 bytes  File  Size = 1096122814 *
*        :          : Tree compression factor =   1.67                       *
******************************************************************************
*Branch  :TEvtHeader                                                         *
*Entries :    50000 : BranchElement (see below)                              *
*............................................................................*
*Br    0 :TObject   : BASE                                                   *
*Entries :    50000 : Total  Size=    1400739 bytes  File Size  =      73005 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=   9.59     *
*............................................................................*
*Br    1 :m_eventId : Int_t                                                  *
*Entries :    50000 : Total  Size=     400741 bytes  File Size  =      69695 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=   2.87     *
*............................................................................*
*Br    2 :m_runId   : Int_t                                                  *
*Entries :    50000 : Total  Size=     400727 bytes  File Size  =       1083 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression= 184.74     *
*............................................................................*
*Br    3 :m_time    : UInt_t                                                 *
*Entries :    50000 : Total  Size=     400720 bytes  File Size  =     112454 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=   1.78     *
*............................................................................*
*Br    4 :m_eventTag : UInt_t                                                *
*Entries :    50000 : Total  Size=     400748 bytes  File Size  =      49392 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=   4.05     *
*............................................................................*
*Br    5 :m_flag1   : UInt_t                                                 *
*Entries :    50000 : Total  Size=     400727 bytes  File Size  =      88500 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=   2.26     *
*............................................................................*
*Br    6 :m_flag2   : UInt_t                                                 *
*Entries :    50000 : Total  Size=     400727 bytes  File Size  =     100763 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=   1.99     *
*............................................................................*
*Branch  :EventNavigator                                                     *
*Entries :    50000 : BranchElement (see below)                              *
*............................................................................*
*Br    7 :TObject   : BASE                                                   *
*Entries :    50000 : Total  Size=    1400739 bytes  File Size  =      73005 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=   9.59     *
*............................................................................*
*Br    8 :m_mcMdcMcHits : multimap<int,int>                                  *
*Entries :    50000 : Total  Size=    1766509 bytes  File Size  =     158609 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=   5.57     *
*............................................................................*
*Br    9 :m_mcMdcTracks : multimap<int,int>                                  *
*Entries :    50000 : Total  Size=   68397115 bytes  File Size  =    2343546 *
*Baskets :       21 : Basket Size=    3200000 bytes  Compression=  27.82     *
*............................................................................*
*Br   10 :m_mcEmcMcHits : multimap<int,int>                                  *
*Entries :    50000 : Total  Size=    1412397 bytes  File Size  =      77370 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=   9.12     *
*............................................................................*
*Br   11 :m_mcEmcRecShowers : multimap<int,int>                              *
*Entries :    50000 : Total  Size=   44223105 bytes  File Size  =    4505469 *
*Baskets :       13 : Basket Size=    3200000 bytes  Compression=   9.11     *
*............................................................................*
*Branch  :TMcEvent                                                           *
*Entries :    50000 : BranchElement (see below)                              *
*............................................................................*
*Br   12 :TObject   : BASE                                                   *
*Entries :    50000 : Total  Size=    1400739 bytes  File Size  =      73005 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=   9.59     *
*............................................................................*
*Br   13 :m_mdcMcHitCol : TObjArray*                                         *
*Entries :    50000 : Total  Size=    2900781 bytes  File Size  =      96775 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=  14.98     *
*............................................................................*
*Br   14 :m_emcMcHitCol : TObjArray*                                         *
*Entries :    50000 : Total  Size=    2900781 bytes  File Size  =      96775 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=  14.98     *
*............................................................................*
*Br   15 :m_tofMcHitCol : TObjArray*                                         *
*Entries :    50000 : Total  Size=    2900781 bytes  File Size  =      96775 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=  14.98     *
*............................................................................*
*Br   16 :m_mucMcHitCol : TObjArray*                                         *
*Entries :    50000 : Total  Size=    2900781 bytes  File Size  =      96775 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=  14.98     *
*............................................................................*
*Br   17 :m_mcParticleCol : TObjArray*                                       *
*Entries :    50000 : Total  Size=  214293808 bytes  File Size  =   88259473 *
*Baskets :       67 : Basket Size=    3200000 bytes  Compression=   2.39     *
*............................................................................*
*Branch  :TDstEvent                                                          *
*Entries :    50000 : BranchElement (see below)                              *
*............................................................................*
*Br   18 :TObject   : BASE                                                   *
*Entries :    50000 : Total  Size=    1400739 bytes  File Size  =      73005 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=   9.59     *
*............................................................................*
*Br   19 :m_emcTrackCol : TObjArray*                                         *
*Entries :    50000 : Total  Size=  137672671 bytes  File Size  =  102623251 *
*Baskets :       43 : Basket Size=    3200000 bytes  Compression=   1.31     *
*............................................................................*
*Br   20 :m_mdcTrackCol : TObjArray*                                         *
*Entries :    50000 : Total  Size=   54192613 bytes  File Size  =   40240017 *
*Baskets :       17 : Basket Size=    3200000 bytes  Compression=   1.27     *
*............................................................................*
*Br   21 :m_tofTrackCol : TObjArray*                                         *
*Entries :    50000 : Total  Size=  325052388 bytes  File Size  =  116054748 *
*Baskets :      101 : Basket Size=    3200000 bytes  Compression=   2.77     *
*............................................................................*
*Br   22 :m_mucTrackCol : TObjArray*                                         *
*Entries :    50000 : Total  Size=   13866164 bytes  File Size  =    2992957 *
*Baskets :        4 : Basket Size=    3200000 bytes  Compression=   3.58     *
*............................................................................*
*Br   23 :m_mdcDedxCol : TObjArray*                                          *
*Entries :    50000 : Total  Size=   31490685 bytes  File Size  =   16069844 *
*Baskets :        9 : Basket Size=    3200000 bytes  Compression=   1.76     *
*............................................................................*
*Br   24 :m_extTrackCol : TObjArray*                                         *
*Entries :    50000 : Total  Size=  252927415 bytes  File Size  =  164009341 *
*Baskets :       79 : Basket Size=    3200000 bytes  Compression=   1.52     *
*............................................................................*
*Br   25 :m_mdcKalTrackCol : TObjArray*                                      *
*Entries :    50000 : Total  Size=  395104659 bytes  File Size  =  342192781 *
*Baskets :      123 : Basket Size=    3200000 bytes  Compression=   1.15     *
*............................................................................*
*Branch  :TEvtRecObject                                                      *
*Entries :    50000 : BranchElement (see below)                              *
*............................................................................*
*Br   26 :TObject   : BASE                                                   *
*Entries :    50000 : Total  Size=    1400739 bytes  File Size  =      73005 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=   9.59     *
*............................................................................*
*Br   27 :m_evtRecEvent : TEvtRecEvent*                                      *
*Entries :    50000 : Total  Size=    4800781 bytes  File Size  =     586057 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=   4.10     *
*............................................................................*
*Br   28 :m_evtRecTrackCol : TObjArray*                                      *
*Entries :    50000 : Total  Size=   57904763 bytes  File Size  =    7906090 *
*Baskets :       18 : Basket Size=    3200000 bytes  Compression=   6.92     *
*............................................................................*
*Br   29 :m_evtRecPrimaryVertex : TEvtRecPrimaryVertex*                      *
*Entries :    50000 : Total  Size=    9908973 bytes  File Size  =    3494364 *
*Baskets :        3 : Basket Size=    3200000 bytes  Compression=   1.95     *
*............................................................................*
*Br   30 :m_evtRecVeeVertexCol : TObjArray*                                  *
*Entries :    50000 : Total  Size=  245430114 bytes  File Size  =  203133314 *
*Baskets :       76 : Basket Size=    3200000 bytes  Compression=   1.19     *
*............................................................................*
*Br   31 :m_evtRecPi0Col : TObjArray*                                        *
*Entries :    50000 : Total  Size=    2900788 bytes  File Size  =      96760 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=  14.99     *
*............................................................................*
*Br   32 :m_evtRecEtaToGGCol : TObjArray*                                    *
*Entries :    50000 : Total  Size=    2900816 bytes  File Size  =      96774 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=  14.98     *
*............................................................................*
*Br   33 :m_evtRecDTagCol : TObjArray*                                       *
*Entries :    50000 : Total  Size=    2900795 bytes  File Size  =      96786 *
*Baskets :        1 : Basket Size=    3200000 bytes  Compression=  14.98     *
*............................................................................*

I want to read the last branch,which is named m_evtRecDTagCol but the TObjArray* I read is empty. I read the branch like this:

TEvtRecObject *p1=new TEvtRecObject();
t->GetEntry(1);
TObjArray *a=p1->getEvtRecDTagCol();

But a is empty.I just want to know where the data is stored in this branch,I can’t find it.

TEvtRecObject is no need to SetBranchAddress.

I think @pcanal can help you.

Can anyone help me ?

What do you mean? How is the TTree giving you access to the data?