ROOT Analysis code with friend TTree's

[muanza]

Hello,

I'd like to use MC truth infos from the GEN TTree within an analysis code based upon a MakeClass defined on the Analysis TTree.

I have no experience with friend TTree's, so I'd like to know if someone has a running example.

Thanks
Regards, Steve

[Pavel Demin]

Hi Steve,

Do you really need to use MakeClass? If it's so, I'm afraid we don't have any example showing how to use MakeClass and AddFriend.

Otherwise, there is a basic example in the ExRootAnalysis repository that uses ExRootTreeReader and AddFriend:

​https://server06.fynu.ucl.ac.be/projects/ExRootAnalysis/browser/trunk/test/AddFriendExample.C

You can find in the attachment a version of this script adapted to the Delphes ROOT tree format.

You can compile and run this example using the following commands:

g++ -O2 -m32 -I. -IUtilities -Llib -lUtilities `root-config --cflags --libs` AddFriendExample.cpp -o AddFriendExample
export LD_LIBRARY_PATH=./lib
./AddFriendExample

Alternatively, there is an example that comes with the Delphes code that show how to analyze reconstructed and generated objects without using AddFriend. It uses 3 ExRootTreeReader objects to read Analysis, GEN and Trigger trees in parallel. Here is a list of relevant files:

Examples/Analysis_Ex.cpp
Examples/interface/Analysis_Ex.h
Examples/src/Analysis_Ex.cc

Regards,

Pavel

[favereau]

Hi,

Did pavel's solution help ?

Thanks for the report,

Jerome

[muanza@…]

Hello Pavel,

Thanks for this working example. Now I manage to access simultaneoulsy to the different TTrees.

I think this ticket can be closed.

Regards, Steve