First of all, read through the Twiki MiniAOD Workbook.

There are two jet collections stored. They are

• “slimmedJets” = AK4PFJetsCHS
• “slimmedJetsAK8” = AK8PFJetsCHS (has a transverse momentum cut of pT > 100 GeV)

For slimmedJets, b-tag variables are stored, for slimmedJetsAK8 not. Access via

 jet.bDiscriminator("jetBProbabilityBJetTags")

The AK8 collection contains userfloats for the jets pruned, trimmed and filtered mass. Access via

 fatjet.userFloat("ak8PFJetsCHSPrunedLinks")
 fatjet.userFloat("ak8PFJetsCHSTrimmedLinks")
 fatjet.userFloat("ak8PFJetsCHSFilteredLinks")

Flavour is stored for slimmedJets via

 abs(j.partonFlavour())

, not for AK8.