Multiple fastjet runs and b tagging efficiency
Afternoon all,
I have a couple of queries if that's alright. I am generating events with a final state of bb~bb~ (coming from a pair of 2HDM Higgs'), and as a sanity test have totally stripped off all cuts I can find (in the MadGraph run card, and in MadAnalysis code), as well as switching off any radiation of b quarks in the Pythia card. I expect in this case to see therefore my b jet multiplicity to consist entirely of events with four b tagged jets, but this is not the case. In fact I see ~15% of events contain three b jets (so just under 4% of b jets seem to be 'lost').
It has been suggested that this could be down to jets which are poorly reconstructed, and so have some large enough separation to the tagging b hadron, dr > deltaR, so that the internal tagging routine fails (despite me setting b tag efficiency to 1.0). I thought it would be good to get your opinion on whether this could be possible, or if there is any other reason for losing these b jets? We suspected jets were merging but this does not appear to be the case.
My other query, is whether it's possible to design and expert mode analysis containing multiple runs of fastjet (and which codes might need editing to achieve this). In particular we would like to run clustering with a standard cone size, remove a pair of jets based on some criteria, and then recluster the remaining particles with a larger cone size (we hope this will 'regain' the lost b jet with it's neighbour).
Thank you, and apologies for the long query.
Billy
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