Ttbar analysis skeleton
The analysis of the Ntuples for the Rome data was done in ROOT. On this page the Analysis Skeleton is presented and instructions on how to use it.
The 3 files that make up the Analysis Skeleton
The Analysis of the Root ntuple proceeds in a very straightforward way. Inside ROOT we used MakeClass() to get the .h and .C files. These were extended to our needs and together the following three files form the analysis skeleton:
- The standard header file extended with the implementation of a few routines the user is not expected to change often
- The user analysis-file where the user:
- o reads in the event
- o fills vectors with 'good' physics objects (leptons, jets, photons etc. passing the user's quality requirements)
- o performs the top-analysis. The resulting histograms will be written out in a separate root file
3) simpleNtupleTTbarAnalysis.C
- The steering-file containing the location of the ntuples and a function that decides:
- o what ntuples to process (fast/full/background simulation)
- o how many events to process
- o name of the output file
How to run the Analysis Skeleton in ROOT
The first step is to correctly set the location of your ntuples in the file simpleNtupleTTbarAnalysis.C. Then, to analyse the first 100 events in ntuple-set 1 and to store the output histograms in a file called summary_ttbar_full_test.root simply open a root session and type:
Root> .L simpleTTbarAnalysis.C++; Root> .x simpleNtupleTTbarAnalysis.C(1,100,"test");
When setting the number of events to "-1", all events are processed.
Structure of the program
The '.C'-file is documented and should speak for itself. Nevertheless it is always nice to get a little bit more information on the logic behind the program:
step 1) After reading the full event information into memory, we proceed by filling vectors of analysis objects (electrons, muons, photons, jets)
step 2)
step 3)
step 4)
step 5)
What is produced
At the end of the Ntuple, all histograms are written to file