Light Higgs Benchmark Analyses
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Light Higgs Benchmark Analyses Christian Grefe, Tomáš Laštovička , Blai Pie Valls, Jan Strube and Frederic Teubert WG6 Meeting 16/02/2011
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Light Higgs Benchmark Analyses. Christian Grefe, Tomáš Laštovička , Blai Pie Valls, Jan Strube and Frederic Teubert WG6 Meeting 16/02/2011. Channels Summary. H→ μμ Very rare decay (≈5.10 -4 ) Difficult to observe at the LHC (3 σ for 300fb -1 ) Clear signature – two muons H→bB - PowerPoint PPT Presentation
Transcript of Light Higgs Benchmark Analyses
Light Higgs Benchmark AnalysesChristian Grefe, Tomáš Laštovička, Blai Pie Valls,
Jan Strube and Frederic Teubert WG6 Meeting 16/02/2011
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Channels Summary
H→μμ– Very rare decay (≈5.10-4)– Difficult to observe at the LHC (3σ for 300fb-1)– Clear signature – two muons
H→bB– Two jets, missing energy– High branching ratio to b-quarks (120GeV Higgs) ≈80%
– Both forward region dominated, Higgs produced by WW fusion– Main sources of background: WW-fusion-to-Z and WW+ZZ– No event overlay in the following
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H→μμBlai Pie Valls
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Summary (and reminder) I.
not checked yet
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Summary (and reminder) II.
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Higgs Invariant Mass
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Z0 Invariant Mass
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Z0 Invariant Mass In Higgs Window
More events produced. To be updated…
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H→bbTomáš Laštovička
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Samples and Event Selection
Samples– Signal (HbB): 1300 events (of 20k simulated)
/castor/cern.ch/grid/ilc/user/c/cgrefe/clic_sid_cdr/ee_h_bb/slicPandora/
– Background (qQ via Z): 440 events (due to castor)
/castor/cern.ch/grid/ilc/user/c/cgrefe/clic_sid_cdr/ee_z_mumu/fullReco/
Selection– Photons with large energy E>60GeV removed– Photons with E>5GeV at shallow angles removed (likely ISR photons)– Remaining ReconstructedParticles forced into two jets– Invariant mass reconstruction resolution crucial for background suppression.
• In fact, no jet clustering needed at this step• no jet flavour tag yet
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Event Classification
Similar to H→μμ analysis, events classified in 3 categories1. Both jets are central (CC)
2. At least one central jet (C+)
3. Both jets are forward (FF)
Separation Central/Forward based on jet polar angle – 38 - slightly higher than for μμ
DISCLAIMER:
There was a number of bug fixes to Whizard, Pandora and LCIO very recently. Plots to be updated in the following weeks.
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CC
FF
C+
Higgs Mass Reconstruction
Higgs mass reconstruction has a very poor resolution even when both jets are central.
Peaky structure visible– not seen by Marcel in his x-check plots
How does Z-peak look like?
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Marcel’s Cross-check
The same event sample, (almost) identical RP selection cuts. Different x-range and binning, but the peaky structure does not seem to be
there for both jets in the central barrel (left).
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CC
FF
C+
Z0 Mass Reconstruction (qqlight_nunu)
Something is terribly wrong here…
… let’s see these plots after reconstruction code bug fixes.
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Polar Angle and pT Distributions
HbBqQ (light)
qQ (light) HbB
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ISR Bug in Whizard 1.95
Found – thanks to Tim – when looking at the Higgs mass reconstruction issues. Event center-of-mass energy calculated without without taking into account the
transverse momentum of the ISR photons
Tim provided a fix (whizard-src/events.f90) to Stephan– see Stephan’s talk for more info regarding impact on MC generation– almost all samples affected and need to be re-generated
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Outlook
A number of updates and bug fixes found recently:– Pandora– Whizard 1.95– LCIO
Samples to be re-generated and re-reconstructed– which will hopefully solve the presented issues.
