Hi,
I’m trying to do the 4leptons analysis with ATLAS data15+16, but parts of MC backgrounds process are missing, for example: ODEO_FEB2025_v0_exactly4lep_mc_302523.Pythia8EvtGen_A14NNPDF23LO_2DP20_Mass_250_400.exactly4lep.root; it only contains 1.4KB and no tree called "analysis’’ in the root file. Does anyone met this problem ? Thank you.
Best,
Lee.
Empty files like that typically indicate that no events passed the selection. In the case you named, this is a diphoton process with an invariant mass cut on the photons between 250 and 400 GeV, and the skim requires at least four good leptons in the event. That just means there aren’t any events in that sample with at least four good leptons. If you check the “noskim” version of the dataset, you’ll see quite a few events, and you can look at how the cuts affect the number of events available to see what removes most of them.
Best,
Zach