July 13, 2006FTK Meeting3 Sherpa samples Last meeting, thought final samples were being generated. Several problems uncovered since then.
July 13, 2006FTK Meeting4 Sherpa problem #1 2 2-only sample (red) is harder than 2 2+2 3 (green)! Problem in sherpa 1.0.8—parton shower starting scale not clearly defined for 2 2 alone.
July 13, 2006FTK Meeting5 Drop 2 2 ME in sherpa All the physics processes we look at so far have 4 final state objects. In a 2 2+2 3 sample, events produced by the 2 2 ME contribute negligibly to trigger rates. Drop 2 2 ME to increase effective statistics.
July 13, 2006FTK Meeting6 Sherpa problem #2 (related to #1?) Sample without 2 2 ME has harder 4 th jet. 4 th jet is produced by PS in either case—expect very similar distributions. Plots normalized by cross-section. Events per pb -1
July 13, 2006FTK Meeting7 Sherpa problem #3 (from Kohei) Lowering the y cut of the sample should only increase the derived trigger rate by covering more phase space. But rate(y cut =10) < rate(y cut =25)! Related to other problems? Revisit with recent fixes.
July 13, 2006FTK Meeting8 Additional sherpa questions Execution time in my setup is longer than the authors see. Strangely, t(MI-on) < t(MI-off). Why not throw this all out the window and use Pythia or Alpgen? –Point was to avoid pythia dijet+PS to describe 3 rd, 4 th jets. But pythia can and should be used as a baseline to compare to. Help from Kohei for jobOptions. –Alpgen is complicated in different ways. SUSY folk are trying to get a validated multijet sample out of it. Could be an option.
July 13, 2006FTK Meeting9 LVL1 parametrization For BG processes with real s, would be useful to have parametrization of LVL1 trigger response to s. Improvements in ATLAS DDM mean I can access datasets… –SingleTaupt20, 50, 100 copied over. –Can’t use samples with filters! Next step is to run full latest simulation and make response plots for matched s.
July 13, 2006FTK Meeting10 Multi-threshold machinery Rigorous determination of the probability for a given event to pass a given set of jet trigger thresholds (given the LVL1 jet jet parametrizations) is somewhat complicated. Code available now for the general case at: http://hep.uchicago.edu/~brubaker/ftk/
July 13, 2006FTK Meeting11 LVL1 rates for H hh 4b Example threshold scan, two thresholds, using full parametrization machinery. Valid for any 4-jet FS. Uses Sherpa MC with known bug rates too low! 1 st & 2 nd jet threshold 406080100 403.0±0.62.2±0.41.6±0.41.1±0.3 600.035±0.0130.031±0.0090.023±0.008 80(5±3)e-5(4±1)e-5 100(4±2)e-9 3 rd & 4 th jet threshold Bad MC! Rate @ 10 33 cm -2 s -1
July 13, 2006FTK Meeting12 Plans Make and check “final” sherpa samples. Use pythia sample as bg rate cross-check. Make LVL1 parametrization. Understand H hh 4b cross-section vs m H, m h. Perform threshold scans and optimize observation significance for H hh 4b with and without FTK. Focus, finish, document by July 26.