i found this formula W = σL/N. where σ is the cross section , L luminosity and N total no of events generated, but this would be the weight i calculated, not the weight of the mc sample generated,
sorry im very confuse can anyone give me a suggestion, thanks
Hi,
This seems to be a MC specific question and not a ROOT question.
If you want to re-weight different MC samples for the same luminosity, the formula above is the correct one to apply an overall weight to your MC sample that you can pass in TMVA in the DataLoader::AddBackgroundTree or AddSignalTree function.
In some case you need to apply a weight for each event. This weight can be produced for example by your MC generator and you provide in TMVA, using the function, DataLoader::SetBackgroundWeightExpression or SetSignalWeightExpression