A Experimental Details Datasets

For the standard EBM, we train on 300,000 simulated QCD jets. For the hybrid model EBM-CLF, we train on 300,000 simulated Standard Model jets (100,000 QCD jets, 100,000 boosted jets originating from the W boson, and 100,000 boosted jets originating from the top quark). For OOD detection test sets, we employ the hypothetical Higgs boson (in the decay mode of H hh (b b)(b b)) with a mass of 174 GeV, which decays into two lighter Higgs bosons of 80 GeV. All the jet samples are generated with a pipeline of physics simulators. QCD jets are extracted from QCD di-jet events that are generated with MadGraph [4] for LHC 13 TeV, followed by Pythia8 [61] and Delphes [18] for parton shower and fast detector simulation.