Update on Tools FTK Meeting 06/06/06 Erik Brubaker U of Chicago

June 6, 2006FTK Meeting2 Physics Case (Reminder) Statement #1 FTK vs TDR menus, i.e. no tracking at LVL2—ignore timing. Statement #2 FTK vs nominal LVL2, incl. tracking. Need: FTK allows b-jet (  ) ID w/  b,  c,  q,  . Correlation w/ offline? Depends on environment LVL1 trigger rate, driven by multijet evts, estimated using modern generator + parametrization of full ATLAS LVL1 simulation. Fix LVL2 output rate. Limit LVL1 output rate to sth reasonable. Optimize LVL1 cuts & LVL2 tagging reqs, maximizing signal acceptance/ significance. Same as stmt #1, but add trigger timing into the eqs. Hard to estimate, large uncertainties. But more realistic, stronger case. This talk

June 6, 2006FTK Meeting3 Tools needed to estimate LVL1 rates 1.Multijet Monte Carlo with accurate treatment of 3 rd /4 th jets  SHERPA. –Run through ATLFAST fast simulation. 2.Parametrization of LVL1 jet & tau trigger response using full simulation. 3.Code to apply arbitrary set of trigger thresholds to a given event, determine probability (weight) for the event to pass.

June 6, 2006FTK Meeting4 Sherpa issues Several issues discovered with Sherpa samples: –No b quarks in ME Clearly important for tagging rates. Fix next slide. –No underlying event/mult. parton interactns (known) Could be important, falling spectrum and all that. Off by default in Sherpa, bugs/crashes when it’s turned on. Improved by upgrading to last month’s Sherpa release. Still under validation, so not in time for default samples. –Some warnings + rare crashes fixed by upgrading to Sherpa

June 6, 2006FTK Meeting5 Sherpa: b quarks in ME No b quarks in ME for previously produced Sherpa samples. Can add massive b quark by explicitly writing out all processes: –2->2: 8 processes. –2->3: 10 processes. –2->4: 14 processes. Or declare b quark massless and it comes for free with other quarks. Test samples of each: no difference in kinematics, so use easier/quicker massless b approach. But b jets are now clearly more numerous and harder.

June 6, 2006FTK Meeting6 Final Sherpa samples Use Sherpa 1.0.8, massless b quarks in the ME, UE off. (But in parallel work on validating a sample with UE to determine effect.) –2   3 ME, y cut  25 GeV. –Sample with 2  4 is running, but takes much longer. Additional samples can be created as needed. –E.g. tried y cut  10 GeV, but found difficult to use since effective statistics are miserable, and understanding of low-p T jets/triggers is shaky at best.

June 6, 2006FTK Meeting7 Tau LVL1 trigger parametrization Two pieces –Probability to pass iso cuts (2 GeV EM & HAD) –Energy of LVL1 cluster passing iso cuts This characterizes the response of the LVL1 tau trigger to jets. Would be useful to have as well the response to real taus.

June 6, 2006FTK Meeting8 Tau LVL1 parametrization Histograms are dijet MC samples, tau trigger response for slices of ATLFAST jet p T. Curves are from the fitted parametrization. Good (enough) agreement in both prob to pass isolation cuts and energy response. Param valid for ATL p T >10, LVL1  E T >10.

June 6, 2006FTK Meeting9 Jet LVL1 parametrization Response in slices of ATL p T. (From earlier talk)

June 6, 2006FTK Meeting10 LVL1 parametrization Have characterization of jet  jet, jet  tau. –Would be useful to know tau  tau. Have code that, given the parametrization and a list of jets for one event, returns the probability that N of the jets pass a given trigger threshold. –Should extend it to multiple thresholds.

June 6, 2006FTK Meeting11 Conclusions LVL1 rate tools are mostly final. –Took a long time, but was also my introduction to doing analysis/software work in ATLAS. –Work on Sherpa can perhaps be used by rest of ATLAS. Write up the tools as part of FTK physics case note. Focus on physics channel (H  hh  bbbb) for next time.