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tth (h  bb) roadmap

tth (h  bb) roadmap. Chris Collins-Tooth 9-Oct-2007. Introduction. CMS problems [CMS-NOTE-2006/119]: Background Uncertainty b-tagging performance. tt+jets: “the first step”. Aim: 2009/10 for this physics measurement (critical backgd). Sarah & Kenny looking at new MC samples.

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tth (h  bb) roadmap

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  1. tth (hbb) roadmap Chris Collins-Tooth 9-Oct-2007

  2. Introduction • CMS problems [CMS-NOTE-2006/119]: • Background Uncertainty • b-tagging performance

  3. tt+jets: “the first step” • Aim: 2009/10 for this physics measurement (critical backgd). • Sarah & Kenny looking at new MC samples. • Modelling with Alpgen, MC@NLO, Sherpa. • Initial investigation also made by JB DeVivie • There are discrepancies btw. Alpgen / MC@NLO • Normalisation, additional jet rates will be measured (Kenny). • Lepton triggers: day 0 with Z’s? (Samir & Mary?). • Light jets: scale & resolution (Arthur [watch jet/Etmiss]?) • B-tagging (Sasha? + Kenny?): Rj critical. • eb /Rj working point depends on s(ttjj) and s(ttbb).

  4. tt+bb • Need to evalutate experimentally as theory is too uncertain! • TRF and anti-correlation (anti-btag) to be evaluated (Marseille[TRF] Glasgow [anti-btag])?) • For CSC note, MC sim done in AcerMC: LO, [QCD,EW], • Also available in Alpgen (Sarah, Kenny) • Overlap removal with MC@NLO ttbb difficult. • Consult MC group.. • Very sensitive to QCD Scale (~50%), PDFs (~5%). • ttbb is a multi-scale process (t,b), ttjj one scale (t).

  5. Signal tth (hbb) • Long term effort: 30fb-1, which implies 2010/2011. • CSC note is a first step, aim complete Dec’07. • 2 (maybe 3) final states under consideration: • Semi-leptonic (traditional final state). • Fully-hadronic (dependent on trigger) Saverio, Genoa group. • Fully-leptonic (nobody working on this yet!). • For semi-leptonic: • Trying cut-based (Me, Bill Murray with constrained mass fit). • Multivariate global/pairing likelihood (Marseille). • NN (Helen, Me) on semi-leptonic final state. • B-tagging important: (eb)4 & there are light jets too (Rj)2. (Sasha? Kenny?) • Light Jets: scale & resolution (Arthur?) • B Jets: scale & resolution, must be treated separately to light jets. • Critical to stay connected with performance groups. • This channel involves e/gamma, flavour tagging, jet/ET miss, top!! • Info does not yet flow from perf. groups to analyses smoothly. • Would like representatives to go to all these meetings! • For the future: • Possibility to disentangle tth(hbb) from ttjj/ttbb with Matrix Element MC (Samir?) • Combination of low-mass channels (Cath, Samir)

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