Update on Tools

1
Update on Tools

• FTK Meeting
• 06/06/06
• Erik Brubaker
• U of Chicago

2
Physics Case (Reminder)
Statement 1 FTK vs TDR menus,i.e. no tracking
atLVL2ignore 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.
This talk
3
Tools needed to estimate LVL1 rates

• Multijet Monte Carlo with accurate treatment of
  3rd/4th jets ? SHERPA.
• Run through ATLFAST fast simulation.
• Parametrization of LVL1 jet tau trigger
  response using full simulation.
• Code to apply arbitrary set of trigger thresholds
  to a given event, determine probability (weight)
  for the event to pass.

4
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 its
  turned on.
• Improved by upgrading to last months Sherpa
  release.
• Still under validation, so not in time for
  default samples.
• Some warnings rare crashes fixed by upgrading
  to Sherpa 1.0.8.

5
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-gt2 8 processes.
• 2-gt3 10 processes.
• 2-gt4 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.

6
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?2 2?3 ME, ycut ? 25 GeV.
• Sample with 2?4 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.

7
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.

8
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 pTgt10, LVL1 t ETgt10.

9
Jet LVL1 parametrization
Response inslices ofATL pT.
(From earliertalk)
10
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.

11
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.