1. FTK Studies: H  hh  bbbb FTK Physics Case Meeting 11/03/05 Erik Brubaker University of Chicago

2. Nov 3, 2005FTK Physics Case Meeting2 Organization Web page here: http://hep.uchicago.edu/~brubaker/ftk/ http://hep.uchicago.edu/~brubaker/ftk/ –Links to previous meetings –Mailing list –Information about tools, e.g. L1 response parameterizations –Analysis code snippets, e.g. jet trigger combinatorics –Collect useful plots, results

3. Nov 3, 2005FTK Physics Case Meeting3 Topics H  hh  bbbb process, signal sample SHERPA multijet background sample Some event rates Next steps

4. Nov 3, 2005FTK Physics Case Meeting4 Reminder: Strategy Making the physics case for FTK means studying signal and background trigger rates for several processes. For now, quantify improvements as a function of increase in L1 rate. –In parallel, studies of FTK speed and efficiency will tell us the magnitude of that increase. Use fully simulated events to parameterize the L1 jet and tau trigger response vs ATLFAST jet p T. Then various processes for physics studies can be studied using ATLFAST.

5. Nov 3, 2005FTK Physics Case Meeting5 Response parameterization Functional form: tried & true double Gaussian. –No pathological behaviors –Second Gaussian can take care of high tails (?) Can be modified & improved as needed.

6. Nov 3, 2005FTK Physics Case Meeting6 Double Higgs—Process Resonant production of lightest MSSM neutral scalar Higgs h 0 through the heavier H 0. Previous study (ATL-PHYS-97-104) –For M H =300 GeV and tan(  =3, S/sqrt(B) of 5.7 can be reached using 300 fb -1 ; this requires 4 jets with E T >40 GeV and |  |<2.5. –For lower integrated luminosity, more tricks are needed and jets down to 20 GeV are preferred. –They concluded trigger rates probably prohibitive.

7. Nov 3, 2005FTK Physics Case Meeting7 Signal Sample Contrary to last time’s claim, one can use Pythia for resonant H  hh production. –m H = 300 GeV –m h = 130 GeV –Pythia reports  = 2 fb Not sure I’m working in a consistent MSSM world. Earlier studies used low tan  (so lower m h ), and  ≈ 2 pb. Generated 10M events, so far only fast simulation. Should check sensitivity to m H, m h.

8. Nov 3, 2005FTK Physics Case Meeting8 Signal sample Quite low jet p T, especially for j4. Probably want multiple trigger thresholds.

9. Nov 3, 2005FTK Physics Case Meeting9 SHERPA event generator Many of our processes have backgrounds with four jets in the final state. –Want accurate ME description of kinematics. SHERPA: developed by Dresden group. –http://www.physik.tu-dresden.de/~krauss/hep/http://www.physik.tu-dresden.de/~krauss/hep/ Generator of generators, like CompHEP etc. Handles consistently boundary between matrix element and parton shower emissions. Produces unweighted events. Not widely used, tested in ATLAS.

10. Nov 3, 2005FTK Physics Case Meeting10 SHERPA multijet sample Unexpected distributions of njet, jet p T. Expected higher for higher-order ME— opposite is true. PS/ME boundary is set to 50 GeV.

11. Nov 3, 2005FTK Physics Case Meeting11 SHERPA multijet sample No obvious “turn-on” of add’l jets from ME.

12. Nov 3, 2005FTK Physics Case Meeting12 Signal & Background L1 rates Use fast simulated signal & SHERPA samples. –Want Pythia dijets too, but these are more complicated. Require at least 4 ATLFAST jets inside |  |<2.8. Find the probability for the event to have four jets passing a 40 (60, 80, 100) GeV trigger. –Want multiple trigger thresholds as well, but that is more complicated.

13. Nov 3, 2005FTK Physics Case Meeting13 Beginnings of an L1 rate table SampleSignalPyth dijetSHERPA x-section2 pb24.6 ub N Events110k10k Eff, #/fb -1 405.8%,1160.17%, 42M 601.7%, 340.049%, 12M 800.64%, 130.022%, 5.4M 1000.29%, 60.012%, 3M

14. Nov 3, 2005FTK Physics Case Meeting14 Next steps Get full simulation of H  hh  4b. –Check that L1 response param. matches observed rate –Work out analysis more thoroughly—need to determine improvement from FTK relative to some “state of the art”. Generate large SHERPA multijet sample. What other background samples are needed? Revisit L1 response—improve as needed.