Trouble while running root file from Event Generator

[Cauê Evangelista de Sousa]

Hi, guys!

I'm trying to simulate the CMS detector using a .root file from Madgraph. The name of the Tree structure inside this file is LHEF, wich is the default name of the Trees generated by Madgraph.

I tried to run the simulation using the command

./DelphesROOT delphes_card_CMS.tcl output.root input.root

but I received the following error massage:

Error in <TChain::LoadTree>: Cannot find tree with name Delphes in file input.root

Question: is there no way to open a tree with a differente name? Of course, I can change the name of the tree inside the input file, but I was wondering if I can solve this in Delphes.

[Pavel Demin]

Question: is there no way to open a tree with a differente name? Of course, I can change the name of the tree inside the input file, but I was wondering if I can solve this in Delphes.

Just change the name of the tree on line 120 in DelphesROOT.cpp. However, it's possible that the format of the tree isn't what DelphesROOT.cpp expects.

Moreover, the LHEF tree name indicates that this tree contains only partons. I think that this file should be processed with Pythia or Herwig before processing it with Delphes.

As far as I know, when using Delphes with MadGraph, the processing chain should look like the following:

MadGraph -> MadEvent -> Pythia or Herwig -> Delphes

Normally, Pythia or Herwig output HepMC files. So, the DelphesHepMC reader should be used to read these HepMC files.

[Cauê Evangelista de Sousa]

Hi, Pavel.

Thank you very much!

When running Madgraph, I switched the shower/hadronization program option to Pythia, so I think that the tree has already passed though Pythia, but I will verify this.

Again: thank you very much.