WG1 - kick-off meeting on YR5 activities

4/S-030 (CERN)



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Alessandro Calandri (Eidgenoessische Technische Hochschule Zuerich (CH)), Alexander Karlberg (CERN), Bernhard Mistlberger (SLAC National Accelerator Laboratory (US)), Hannah Arnold (Stony Brook University)
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Alexander Karlberg
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Hannah Arnold
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  • sl 10: work ongoing, and planned for YR5. All projects are well covered for the signal processes, however this is not the case for the background processes, here ideas are present (sl 17) but person power is needed. Important to contact ttH conveners on this

Gluon fusion

  • sl 2: plan to include updated numbers with top mass correction and mixed predictions for m_t/m_b for YR5? Yes
  • sl 2: can you elaborate on Hcc boosted? Ideally release predictions for Hcc boosted uncertainties and BR. Need discussion with BR group
  • sl 2: N3LO PDF - check on whether it is relevant to change recommendations for central values. Groups working on N3LO PDF updates have been contacted and will present together in dedicated gluon fusion meeting (worth advertising this meeting also to the LHC PDF Forum)


  • sl 7: clarification on the table for TH uncertainties for VBF H and ggH in VBF-enriched environment: difference originates from phase-space/kinematics dependency. Uncertainty budget CMS internal scale factors, while ATLAS 2-point systematics plays a large role in uncertainty

  • sl 10: possible to apply same procedure for VH had? No, need of sample specialisation as resonant part is not included in predictions. Tested VH had with VBF cuts: interference does not seem large, could be neglected. However VH (had) along with boosted vector boson and ISR cannot be distinguished from the VBF topology. Start considering process harmonisation: VH leptonic (main target of VH) and VH hadronic 


  • fraction of negative weights for MC@NLO or Sherpa? Not sure, to be cross-checked

  • sl 2: Hcc/Hbb backgrounds from Hgg where gluons in cc/bb (Dalitz-type decay). Are you looking for everything, e.g. both Yukawa’s and Daliz decays (Yukawa couplings are small and gluon contamination has a large BR)? Not included in the modeling, ignored because this contributions doesn’t peak at the Higgs mass (removal with Higgs mass window cut) so not relevant. Worth asking experiments to check gluon contamination  in analysis phase-space as effect might not be negligible.
  • sl 6: uncertainty band for ggZH LO/NLO differential k-factor: internal signal scale variations.

  • sl 6: Higgs doesn’t recoil to hard jet at LO (Higgs and Z are back-to-back). When there’s additional jet, Higgs recoil against it, this explains large k-factor at high ptH. Using double-differential observables with bins in jet pt/Higgs pt, we might be able to suppress this kinematic region where the Higgs recoils against hard jet to mitigate the LO to NLO k-factor in the high ptH tail

  • sl 10: elaborate on plan to reduce complexity on V+jets modeling? Consider less generators to compare and potentially reduce the set of 2-point variations for uncertainties in ATLAS? Scale variations? Still to be fully discussed


  • sl 7: polarisation: is there a study which shows longitudinal polarisation components as a function of the 4l mass, i.e. when you go in the high tails of off-shell? How does the fraction change vs m_4l? Public UFO to produce results - results are not in the paper; Rafael and Suman will follow-up offline for UFO models to produce different polarisation states

  • sl 9: study published a couple of years ago. Is it possible to have it included in YR5? Yes, possible

  • measuring width in model-independent way by Fabrizio’s group - to be discussed/useful for inclusion for YR5. Propose a summary of current results on off-shell as well

There are minutes attached to this event. Show them.
    • 3:00 PM 3:15 PM
      Introduction 15m
      Speakers: Alessandro Calandri (Eidgenoessische Technische Hochschule Zuerich (CH)), Dr Alexander Karlberg (CERN), Bernhard Mistlberger (SLAC National Accelerator Laboratory (US)), Hannah Arnold (Stony Brook University)
    • 3:15 PM 3:30 PM
      ttH/tH report 15m
      Speaker: Malgorzata Maria Worek (Rheinisch Westfaelische Tech. Hoch. (DE))
    • 3:30 PM 3:45 PM
      Gluon-fusion report 15m
      Speaker: Alessandra Cappati (Centre National de la Recherche Scientifique (FR))
    • 3:45 PM 4:00 PM
      VBF report 15m
      Speakers: Gaetano Barone (Brown University), Jiayi Chen (Simon Fraser University (CA)), Mathieu Pellen (University of Freiburg), Silvia Ferrario Ravasio (CERN)
    • 4:00 PM 4:15 PM
      VH report 15m
      Speakers: Suman Chatterjee (Austrian Academy of Sciences (AT)), Dr Valerio Dao (Stony Brook University)
    • 4:15 PM 4:30 PM
      Off-shell report 15m
      Speaker: Raoul Horst Rontsch