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FTK Meeting Summary: Examining Jet Rates, Systematics, and Higgs Decays

Detailed review of jet rates, systematics, and Higgs decay processes discussed in FTK meetings at the University of Chicago. Insights on model consistency, systematics analysis, and recommendations for FTK studies.

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FTK Meeting Summary: Examining Jet Rates, Systematics, and Higgs Decays

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  1. LVL1 rates & Hhh4b Erik Brubaker U of Chicago

  2. Outline • Almost-final word on LVL1 jet rates. • Understanding cross-section for Hhh4b process. • Talk descoped due to UC Tier2 going down last night… FTK Meeting

  3. Jet rates from Sherpa • Check different ME combinations, kT,cut values to balance stats/resources, and to estimate systematics. • LVL1 rates scatter in 40-80 Hz. • “LVL2” rates require 4 tags, have units of mHz! Not too interesting as is. FTK Meeting

  4. Cross-check: jet rates from Alpgen • Samples from Ambreesh/SUSY group. • ALPGEN light jet samples only. • LVL1 rates slightly underestimated • Total rate lower than, but on the order of, Sherpa results. • Caveat: 4- and 5-jet samples ntupled with 0.7-cone jets—inconsistent with parametrizations… FTK Meeting

  5. Cross-check: jet rates from Pythia • Check against Pythia dijets • Generic QCD incl heavy flavor Caveat: DefaultPythia settings forUE etc. have beenunstable… So… 1. Consistency among models? 2. All are consistently lower than TDR rate:200 Hz for 4j@90 GeV, where 90~=60 inour calibration… FTK Meeting

  6. Systematics on LVL1 jet rates • Variations in ycut, ME configurations in Sherpa • RMS of the 12 sample results, weighted by reported stat unc.: 12% • Differences among generators • Alpgen lower, Pythia higher with caveats: 30% for now • Additional possible factors—need to check explicitly? • PDFs • UE/MPI • Parametrizations RMS=13.1 RMS=7.5 FTK Meeting

  7. LVL1 rates conclusion • Need to finish checking effect of UE/MPI in Sherpa, also different pythia settings (MWT2 died on me last night). • Run this by ATLAS trigger gurus. • Any similar recent studies? • Difference w.r.t. TDR understood? Recommendation for FTK studies: Use Sherpa sample with best combination of statistics,ME configuration, and kT,cut for your proposed thresholds.(Best to try more than one.) Use my machinery to calculate rates for a range of thresholds. Assign 35% uncertainty on absolute rate. http://hep.uchicago.edu/~brubaker/ftk FTK Meeting

  8. Example LVL1 rate scan Require 4 jets:1st & 2nd at cuton x-axis;3rd & 4th at cutin legend. 4th jet cutdrives rate—not surprising FTK Meeting

  9. Hhhbbbb sigma*BR • I had a problem with low s*BR (2 fb) reported by pythia for Hhhbbbb w/ mh=130, mH=300. • What MSSM model was pythia assuming? • Turns out Hhh is large only for lowish tanb, and for 2mh<mH<2mt. • To find operating points: • Use mhmax scenario to stay away from LEP direct search limits. • For a given tanb, scan mA to maximize s(ggH) x BR(Hhh) x BR(hbb) x BR(hbb). FTK Meeting

  10. Additional slides

  11. Physics Case (Details) Statement #1 FTK vs TDR menus,i.e. no tracking atLVL2—ignore timing. Statement #2 FTK vs nominal LVL2,incl. tracking. Need: • FTK allows b-jet (t)ID w/ eb, ec, eq, et. • Correlation w/ offline? • Depends on environment • LVL1 trigger rate, drivenby multijet evts, estimatedusing modern generator +parametrization of fullATLAS LVL1 simulation. Fix LVL2 outputrate. Limit LVL1 outputrate to sth reasonable. Optimize LVL1 cuts& LVL2 tagging reqs, maximizing signal acceptance/significance. Same as stmt #1,but add triggertiming into the eqs. Hard to estimate,large uncertainties. But more realistic,stronger case. FTK Meeting

  12. CKKW vs MLM CKKW: 2 parts Reweight ME to reproduce PS behavior for soft emissions. Reject showers that overlap higher-order ME. Boundary is kT,cutor ycut kT,cut2/s. MLM: matching prescription Cluster partons after shower, compare to ME partons. Require each ME parton to match a unique “jet”, else reject event. ALPGEN SHERPA 4p ME 3p ME CKKW MLM FTK Meeting

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