Christian Grefe Tomáš Laštovička Blai Pie Valls Jan Strube and Frederic Teubert WG6 Meeting 16022011 Channels Summary H μμ Very rare decay 510 4 Difficult to observe at the LHC 3 ID: 553073
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Slide1
Light Higgs Benchmark Analyses
Christian Grefe, Tomáš Laštovička, Blai Pie Valls, Jan Strube and Frederic Teubert WG6 Meeting 16/02/2011Slide2
Channels Summary
H→μμVery 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 followingSlide3
H→
μμBlai Pie Valls Slide4
Summary (and reminder) I.
not checked yetSlide5
Summary (and reminder) II.Slide6
Higgs Invariant MassSlide7
Z0 Invariant MassSlide8
Z0 Invariant Mass In Higgs Window
More events produced. To be updated…Slide9
H→
bbTomáš Laštovička Slide10
Samples and Event Selection
SamplesSignal (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 yetSlide11
Event Classification
Similar to H→μμ analysis, events classified in 3 categoriesBoth jets are central (CC)At least one central jet (C+)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. Slide12
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?Slide13
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). Slide14
CC
FF
C+
Z
0
Mass Reconstruction (
qqlight_nunu
)
Something is terribly wrong here…
… let’s see these plots after reconstruction code bug fixes.Slide15
Polar Angle and pT Distributions
H
bB
qQ
(light)
qQ
(light)
H
bBSlide16
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-generatedSlide17
Outlook
A number of updates and bug fixes found recently:PandoraWhizard 1.95LCIOSamples to be re-generated and re-reconstructedwhich will hopefully solve the presented issues.