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LVL1 rates & H hh4b

LVL1 rates & H hh4b. Erik Brubaker U of Chicago. 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…. Jet rates from Sherpa.

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LVL1 rates & H hh4b

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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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