Light Higgs Benchmark Analyses
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Light Higgs Benchmark AnalysesChristian Grefe, Tomáš Laštovička, Blai Pie Valls,
Jan Strube and Frederic Teubert WG6 Meeting 16/02/2011
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
H→μμBlai Pie Valls
Summary (and reminder) I.
not checked yet
Summary (and reminder) II.
Higgs Invariant Mass
Z0 Invariant Mass
Z0 Invariant Mass In Higgs Window
More events produced. To be updated…
Samples and Event Selection
Samples– Signal (HbB): 1300 events (of 20k simulated)
– Background (qQ via Z): 440 events (due to castor)
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
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
There was a number of bug fixes to Whizard, Pandora and LCIO very recently. Plots to be updated in the following weeks.
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?
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).
Z0 Mass Reconstruction (qqlight_nunu)
Something is terribly wrong here…
… let’s see these plots after reconstruction code bug fixes.
Polar Angle and pT Distributions
qQ (light) HbB
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
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.