Well started running root analysis yesterday. Quite a learning curve. Take output from madgraph, run through CMKIN to get ntpls then h2root to get root files. Once in root chain the files together:

root [0] TChain *myChain = new TChain("h101","");
root [1] myChain->Add("*.root");
root [2] myChain->Merge("bigfile2.root")

now open the file up to look at quantities etc.

first put it in a tree:
TTree *T = _file0->Get("h101;1")

then following from this analyise some quantities

(I posted this before but it failed to work :( )