STXS meeting

42/3-002 (CERN)



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Nicolas Berger (Centre National de la Recherche Scientifique (FR)), Frank Tackmann, Lorenzo Viliani (Universita e INFN, Firenze (IT))

ATLAS Contribution

  • Numbers shows on slide 1 are from H->γγ only, extrapolated from the Moriond CONF note


CMS contribution

  • Results are from the ttH(bb) semileptonic mode only; the DNN is not yet optimized to reduce confusion in top/Higgs reconstruction.
  • slide 5: The table shows how each truth bins distributes into each reco bin (each line sums to 1). The non-diagonal terms are much larger here than in the 3-bin case.
  • The 4-bin analysis may be difficult for ttH(bb). However DNN could possibly be improved (ATLAS expects better performance - it would be desirable to have explicit studies/confirmation)



  • ttH binning:
    • Decision to go for Option 1 since smaller bins are safer with respect to future evolution (in particular 200-300 GeV instead of 200-350 GeV). Could merge 200-300 GeV and 300-400 GeV bins if needed.
  • ggF binning:
    • the binning decisions mainly concern the 400-500 GeV region, which is at the transition between the H->γγ/ZZ and H->bb sensitivity regions: H->γγ/ZZ lose sensitivity above 400 GeV while H->bb sensitivity starts around 450 GeV (see slides 3 and 5 in
    • However H->γγ/ZZ is only measured in the 350-600 GeV bin so not clear where the sensitivity stops exactly, and similarly H->bb sensitivity below 450 GeV is not known. Would need more information on sensitivities in this region to understand which solution entails the least extrapolation.
    • ATLAS could have updated H->bb sensitivity estimates soon.
    • Option 1 seems preferable (smaller bins), but this can be revisited depending on the results of the further studies.
  • ggF jet bins:
    • pTJ cut could be relative to the center of the pTH bin, or the event-by-event pTH; should not have much impact since the pTH bins are rather narrow
    • H->WW should be the analysis most affected, some studies would be useful
    • Could consider raising the pTJ cut even in the 120-200 GeV bin


Action items:

  • Would be good to have H->WW studies from ATLAS and CMS: ideally per-pTH optimizations of the pTJ cut; or more simply r distributions for Higgs signal and backgrounds (mainly ttbar) in coarse bins of pTH.
  • also additional H(bb) studies from ATLAS ?

Aim to converge on the gg->H binning at the next meeting, planned for end of August. Will also have a discussion of the variables to report in the diffXS measurements, following up from LH (Pedja will provide the picture of the blackboard in LH...)


There are minutes attached to this event. Show them.
    • 10:00 AM 10:10 AM
      Introduction 10m
      Speakers: Nicolas Berger (Centre National de la Recherche Scientifique (FR)), Frank Tackmann, Lorenzo Viliani (Universita e INFN, Firenze (IT))
    • 10:10 AM 10:30 AM
      Update from ATLAS 20m
      Speaker: Maria Moreno Llacer (Univ. of Valencia and CSIC (ES))
    • 10:30 AM 10:50 AM
      Update from CMS: STXS binning for ttH(bb) 20m
      Speaker: Peter Kramer (KIT - Karlsruhe Institute of Technology (DE))
    • 10:50 AM 11:10 AM