FTK Studies: H hh bbbb FTK Physics Case Meeting 11/03/05 Erik Brubaker University of Chicago.
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Transcript of FTK Studies: H hh bbbb FTK Physics Case Meeting 11/03/05 Erik Brubaker University of Chicago.
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FTK Studies: Hhhbbbb
FTK Physics Case Meeting
11/03/05
Erik Brubaker
University of Chicago
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Nov 3, 2005 FTK Physics Case Meeting 2
Organization• Web page here: 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
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Nov 3, 2005 FTK Physics Case Meeting 3
Topics• Hhhbbbb process, signal sample
• SHERPA multijet background sample
• Some event rates
• Next steps
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Nov 3, 2005 FTK Physics Case Meeting 4
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 pT. Then various processes for physics studies can be studied using ATLFAST.
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Nov 3, 2005 FTK Physics Case Meeting 5
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.
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Nov 3, 2005 FTK Physics Case Meeting 6
Double Higgs—Process• Resonant production of
lightest MSSM neutral scalar Higgs h0 through the heavier H0.
• Previous study (ATL-PHYS-97-104)– For MH=300 GeV and tan(=3, S/sqrt(B) of 5.7 can
be reached using 300 fb-1; this requires 4 jets with ET>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.
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Nov 3, 2005 FTK Physics Case Meeting 7
Signal Sample• Contrary to last time’s claim, one can use Pythia
for resonant Hhh production.– mH = 300 GeV
– mh = 130 GeV
– Pythia reports = 2 fb• Not sure I’m working in a consistent MSSM world.
• Earlier studies used low tan (so lower mh), and ≈ 2 pb.
• Generated 10M events, so far only fast simulation.
• Should check sensitivity to mH, mh.
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Nov 3, 2005 FTK Physics Case Meeting 8
Signal sample• Quite low jet pT,
especially for j4.
• Probably want multiple trigger thresholds.
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Nov 3, 2005 FTK Physics Case Meeting 9
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/
• 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.
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Nov 3, 2005 FTK Physics Case Meeting 10
SHERPA multijet sample• Unexpected distributions
of njet, jet pT.
• Expected higher <njet> for higher-order ME—opposite is true.
• PS/ME boundary is set to 50 GeV.
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Nov 3, 2005 FTK Physics Case Meeting 11
SHERPA multijet sample• No obvious “turn-on” of add’l jets from ME.
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Nov 3, 2005 FTK Physics Case Meeting 12
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.
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Nov 3, 2005 FTK Physics Case Meeting 13
Beginnings of an L1 rate tableSample Signal Pyth dijet SHERPA
x-section 2 pb 24.6 ub
N Events 110k 10k
Eff,#/fb-1
40 5.8%,116 0.17%, 42M
60 1.7%, 34 0.049%, 12M
80 0.64%, 13 0.022%, 5.4M
100 0.29%, 6 0.012%, 3M
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Nov 3, 2005 FTK Physics Case Meeting 14
Next steps• Get full simulation of Hhh4b.
– 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.