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2015:groups:higgs:diff

Discussion on Differential Higgs Cross Section Measurements

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Session 1 discussion
  • Discussion focused on H→gammagamma and H→4leptons (and H→WW)
  • What would be other useful observables and/or corners of phase space that are not currently measured by the experiments?
    • Inclusive variables
      • pT with a finer binning especially in the low pT range once possible
      • phi* probes the low pT phase space region in a different way (experimental resolution should be better for H→4leptons; H→gammagamma to be checked)
      • pTt (redundant with phi*, check which one can be measured better)
    • 0-jet resolution variables (currently measured: pTj, TauCj)
      • Tau(C)j (lower pTj cut important)
      • Tau0
    • 1-jet resolution variables for pTj1/pT(H)/Tauj1 > cut for different cuts (30, 50, 100)
      • pTj1/pTj2 more differentially
      • pT(Hj-system)
      • phi(H-j)
      • Tau1, jetmass
    • 2-jet: CP studies with ggH
      • Delta phijj mapped to full [0, 2pi] (see arXiv:1006.0986)
      • for CP studies in ggH: use loose delta eta_jj cut (some separation between jets, but looser than one would use for VBF studies)
    • While statistics is limited, measurement of the 1st, 2nd moments of distributions is useful
      (binning effects should be investigated).
  • H→WW(→lnulnu)
    • Most promising: 0-jet (smaller uncertainties from ttbar backgrounds)
    • Definition of fiducial region should include cuts on mll and mT
      • mT<mH reduces off-shell component to avoid associated uncertainties (~10%)
    • Interesting measurement: 0-jet cross section as a function of the pT cut in the jet veto, going as low as possible
    • Do not subtract pp→WW contribution to avoid associated uncertainties (quote estimated contribution)
    • Harmonized fiducial cross section measurements between Higgs and SM would be nice
  • Possibility of a measurement of VH?
    • high pT(V) (easier experimentally) or m(VH) (more direct from the theory perspective) would be interesting from the BSM perspective
    • H→bbbar 0-jet selection is likely the most promising, large uncertainties with the present statistics
      • NB: pT(V) and m(VH) very correlated in 0-jet selection
  • Isolation for photons and leptons
    • Some measurements include an isolation requirement for the photons or leptons into the definition of the fiducial region as the isolation efficiency depends on the production mode.
    • Provide corrections from isolated to full phase space in publications, preferably by production mode.
  • Normalized or non-normalized measurements?
    • Potential advantage: reduction of some experimental uncertainties, which will become more relevant when we are no longer dominated by statistical uncertainties.
    • As theoretical predictions are for cross sections, non-normalized cross sections are preferred in general. They also contain more information.
    • If the full experimental covariance matrix is provided, the normalization can be done easily.
  • Information that is useful to include in publications to allow making maximal use of the results
    • cross correlations between different spectra. In addition, it would also be useful to provide the correlation between the differential distributions and the measured total (fiducial) cross section.
    • estimated nonperturbative effects
    • estimated contributions of non-ggH modes
    • acceptance corrections to allow extrapolation from fiducial region to full phase space (for convenience)
  • Background subtraction?
    • Experimentally H→gammma gamma makes more sense fully background subtracted
    • H→ZZ→4l or H→WW→2l2nu could give measurements including irreducible background (with appropriate fiducial phase space definition including eg suitable m4l window in that case)
    • In that case prediction for irreducible background should also be provided to allow theorists to easily subtract it if desired
Session 2 discussion

jet selection anti-kT R=0.4, pt>25-30 GeV, |eta|<4.5

ggF

(|eta|<2.5)

0j : sigma times BR

1j : pT 100,200,(300,400)_mt,overflow

2j : bin in 2j exclusive and 3j inclusive, distributions mjj, Delta eta_jj, Delta Phi_jj

VBF

2j : mjj, Delta eta_jj, Delta Phi_jj

VH

fully leptonic: mVH 300…500, overflow

1l, 0l: mT>200 GeV

ttH

m_T(ttH) …,500,…

2015/groups/higgs/diff.txt · Last modified: 2015/07/14 08:22 by philippe.gras