The Standard Ntuple web site
with ntuple analysis examples, etc. is available as a primary resource for
current information about the ntuples. A link to this site
is also available off of the main WebDocs page.
This page supplements the material available there.
The MCNtuple package contains the ntuple class definitions for the
Monte Carlo truth ntuple, produced as part of production running
and stored in production files ending in .sntp.<release>.root
or .snts.<release>.root in ROOT TTree "NtpMC".
This ntuple stores a subset of mc truth information, derived from the
complete SimSnarlRecord. The files storing the
ntuple data are therefore of smaller size and are more easily accessible
than the full MC truth data stored as SimSnarlRecords
The MC ntuple is especially useful
for end-user analyses interested in summary results. The MC ntuple can also be
used as a starting point in an analysis to select a subset of Snarls
of interest, before turning to the .cand files for a deeper analysis
of just those selected events.
The MC ntuple is analyzable in a "bare" root session, without the
load of minossoft libraries, or alternatively in a loon session. Examples
of this are given on the Standard Ntuple site described above. The ntuple may
be also be read into a subsequent loon job using job control for
further analysis or record selection.
The MC ntuple consists of a record of class type NtpMCRecord, which is
stored in a ROOT TTree of name "NtpMC" with one record per tree entry.
One NtpMCRecord contains the ntuple summary data from one Snarl.
The NtpMC tree is constructed with one main branch of name "NtpMCRecord",
which has been "split" (automatically, specifying the splitlevel in a root
method) to create a branch.subbranch.(...).leaf structure for the NtpMC tree,
such that every leaf stores the data of one ntuple variable of basic data type
The structure of the NtpMC tree can be viewed in a bare root session using the TTree::Print()
command, for example:
//usage: root -bq thisscript.C >& thisscript.log
TFile* file = new TFile("filename.sntp.R1.9.root","READ");
TTree* tree = (TTree*)(file->Get("NtpMC"));
tree -> Print();
The contents of the ntuple can be better understood by looking at
the data members of the top level ntuple class, NtpMCRecord.
TClonesArray* mc; //-> array of NtpMCTruth
TClonesArray* stdhep; //-> array of NtpMCStdHep
TClonesArray* digihit; //-> array of NtpMCDigiScintHit
The NtpMCRecord class stores data members organized as arrays
of objects. The (TClones)Arrays of objects, for example "mc",
represent the different MC Truth entities associated with the
- The mc array contains the mc truth data associated
with the initiating primary(ies).
- The stdhep array contains the
truth associated with the primaries and secondaries generated during
- The digihit array containts the truth data associated
with the energy deposition hits recorded while tracking through the
active detector layers. Note that the digihit array is only written out if
the job module is configured to do so (see below), otherwise the default
is to not fill the digihit array.
Brief descriptions of the data members appearing in the ntuple are given
in the class definition header files alongside the data members, so that
the MCNtuple/*.h files can be a useful introductory resource to the
content of the MC ntuple.
NtpMCRecords are produced by the NtpMCModule defined in MCNtuple/Module.
The SimSnarlRecord is the input data source for constructing
a NtpMCRecord. SimSnarlRecords from a previously produced
.cand.<release>.root file can be used as input to a subsequent job
in which only the NtpMCModule is run to produce ntuples. However, because
the SimSnarlRecord was incomplete prior to R1.10, this process is only
reliable if run on .cand files produced post R1.9.
The output of the NtpMCModule is a NtpMCRecord stored in Mom. The Output
module will store the NtpMCRecord in a tree NtpMC in the user specified
output file, if requested in the job script. The name of the output tree
may be changed by the user from the default NtpMC.
A simple script to run the NtpMCModule to generate a file testNtpMC.root
with tree NtpMC is shown here. The input file for this script should
be a .cand.<release>.root file containing a SimSnarl tree.
The commented out line illustrates how to configure the NtpMCModule to
activate the fill of the digihit array.
// A job to demonstrate how to run the NtpMCModule
// usage: loon -bq thisscript.C <cand filename>
j.Input.Set("Streams=SimSnarl"); // Define the input data streams
// Optionally active fill of NtpMCDigiScintHits in digihits array
j.Path("Demo").Mod("Output").Set("Streams=NtpMC"); // output data stream
j.Path("Demo").Mod("Output").Set("FileName=testNtpMC.root"); // output file
Last Modified: $Date: 2004/10/23 03:02:25 $