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Update on Tools FTK Meeting 06/06/06 Erik Brubaker U of Chicago Physics Case (Reminder) Statement #1 Statement #2 FTK vs TDR menus, i.e. no tracking at LVL2—ignore timing. FTK vs nominal LVL2, incl. tracking. Fix LVL2 output rate. Limit LVL1 output rate to sth reasonable. Optimize LVL1 cuts & LVL2 tagging reqs, maximizing signal acceptance/ significance. June 6, 2006 Need: • FTK allows b-jet (t) ID w/ eb, ec, eq, et. • Correlation w/ offline? • Depends on environment Same as stmt #1, but add trigger timing into the eqs. • LVL1 trigger rate, driven by multijet evts, estimated using modern generator + parametrization of full ATLAS LVL1 simulation. But more realistic, stronger case. Hard to estimate, large uncertainties. This talk FTK Meeting 2 Tools needed to estimate LVL1 rates 1. Multijet Monte Carlo with accurate treatment of 3rd/4th 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, 2006 FTK Meeting 3 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 1.0.8. June 6, 2006 FTK Meeting 4 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, 2006 FTK Meeting 5 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.) – 22 + 23 ME, ycut 25 GeV. – Sample with 24 is running, but takes much longer. • Additional samples can be created as needed. – E.g. tried ycut 10 GeV, but found difficult to use since effective statistics are miserable, and understanding of low-pT jets/triggers is shaky at best. June 6, 2006 FTK Meeting 6 Tau LVL1 trigger parametrization • Two pieces – Probability to pass iso cuts (2 GeV EM & HAD) A Landau ( pT , B, C) D – Energy of LVL1 cluster passing iso cuts 2 Gaus( ETL1, 0 , 1 ) (1 2 ) Exp( ETL1 / 3 ); i p2i PTATL p2i 1 • 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, 2006 FTK Meeting 7 Tau LVL1 parametrization • Histograms are dijet MC samples, tau trigger response for slices of ATLFAST jet pT. • Curves are from the fitted parametrization. • Good (enough) agreement in both prob to pass isolation cuts and energy response. • Param valid for ATL pT>10, LVL1 t ET>10. June 6, 2006 FTK Meeting 8 Jet LVL1 parametrization Response in slices of ATL pT. (From earlier talk) June 6, 2006 FTK Meeting 9 LVL1 parametrization • Have characterization of jetjet, jettau. – Would be useful to know tautau. • 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, 2006 FTK Meeting 10 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 (Hhhbbbb) for next time. June 6, 2006 FTK Meeting 11