H  ZZ channels

1. HZZ channels N. De Filippis - Politecnicoand INFN Bari StathesPaganis  - University of Sheffield 1 N. De Filippis LHC Higgs xsection group, October 22

2. NLO vs LO generators: signal • Itemstobediscussed and solved: • differentialdistributions at NLO vs LO • differentialk-factor vs pt • CMS : • POWHEG vs PYTHIA is in ourplans • MC@NLO vs PYTHIA tobecheckedfrompastreferencesifany • ATLAS : MC@NLO vs PYTHIA tobecheckedfrompastreferences • help fromtheoristsisneededto do a meaningfulcomparison and alsofrom the technicalpointofview •  transversal meeting with ggZ and VBF subgroups to be organized next week

3. NLO vs LO generators: background • Zbb: • checkdistributionofrelevantobservables in NLO vs LO generators (forexampleinvariantmass ofbb (expectedtoshiftversus high mass butwe don’tknowhowmuch ) • CMS: workingwith LO Madgraph (at partonic and leptoniclevel) • in the past ALPGEN wasalsoused (distributiontobechecked) • ATLAS: sherpa + pythia • Question: Which NLO generatortouse ? Referenceby L. Reinaand code implementation in POWHEG expectedsoon • Absolute cross section to be computed with MCFM • ggZZ contribution to be studies in detail  establish good contact with gg2ZZ authors

4. Background estimates from data • Definitionofcontrolregion: • --Zbb: • --enoughdefinedregion (not public results in CMS and ATLAS)  will try to the analysis at the level of leptons and partons…(one Z + loose)…workis in progress with a phdstudent • --predictioncouldbecompletely wrong ifZbb at NLO giveverydifferentdistributionwithrespectto LO crucial point • -- ZZ, ZZ* normalization from inclusive Z: • -- Inclusive Z to ZZ is a simple calculation • -- is that only valid for qq->ZZ ?? • --anyphysicsjustification ?.... • -- can theorists help ?

5. Common cuts Target is: toprovidetheorists the coordinate of the phasephase in whichto work togetcorrect cross sections and theoreticalestimates Wecouldprovide the common selection at the levelofpreselection or after full cuts our idea is to provide a “common” preselection to keep enough phase space fo the background estimate also otherwise too less background at the end of the selection Isolation included or not  we decided to not include because of dependence/sensibility on experimental facts  somehow a loose isolation could be quoted Cuts on impact parameter not needed at the moment

6. Common cuts: 4l • Proposal of common cuts: CMS +ATLAS • * leptons with pt>5 GeV and |eta|<2.5 • * >=3 (4) leptons with pT>5 • * >= 2 leptons with pT>10 • at least two l+l- pairs of identified leptons with opposite charge and matching flavour. • * at least two matching di-lepton pairs with m2l>12 GeV • at least one 4-lepton combination with m4l>100 GeV • 70 < m_12 < 110 GeV ??

7. Common cuts: 2l2nu, 2l2jet, 2l2b NO public results yet

8. Manpower and miscellanea CMS: myself + one PHD (for ZZ/Zbbstudies) …wewouldprobablyneed a experienced POSTDOC to play withgenerators ATLAS: stathes + reisaburo? + 4l people… (anydedicated POSTDOC ?? We agreed to establish a more strict relation with our “generator group” experts Vertical meeting with ggF and VBF subgroup foreseen next week ?