progress on h/abb -> 4b’s channel for the ftk physics case ~ 4jets trigger w/ and w/o ftk ~
DESCRIPTION
Progress on H/Abb -> 4b’s channel for the FTK physics case ~ 4jets Trigger w/ and w/o FTK ~. Kohei Yorita Young-Kee Kim University of Chicago @ the FTK Meeting on October 19 th , 2006. - PowerPoint PPT PresentationTRANSCRIPT
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Progress on H/Abb -> 4b’schannel for the FTK physics case~ 4jets Trigger w/ and w/o FTK ~
Kohei Yorita Young-Kee Kim University of Chicago @ the FTK Meeting on October 19th , 2006
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Review of 4J Trigger (MC)We have looked at many variations of MC samples.> Sherpa - version (patch) change - different configuration - yt cut - w/ and w/o UE> Pythia - v6.2 (v10 Athena) - v6.3 (v11 Athena)
Now it is time to decide “default” sample to conclude studies. (whatever it is, big unknown factors (always) still remain.)
Now Default Sample : SHERPA 2->3, yt>25 ; 10M events
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Systematics on MC ChoiceAgain, Default Sample : SHERPA 2->3, yt>25 ; 10M events
Comparison to 2->2+3+4
10% systematics 5% systematics
Comparison of yt cuts
Correlated & poor stat.
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Comparison to PYTHIA
Pythia 6.2 Pythia 6.3 Old UE/MI New UE/MIPt>15 : +-30% x3~4Pt>20 : +-30% x2~3Pt>50 : +-20% x~1.4> Big Unknown : UE/MI tuning.> Why v6.3 changes so much by Ptcut ?> My Signal sample (H/Abb) is still v6.2. - so we should take +- 30%.
So total is ~32%. Might differ by ~2-3 though.
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Issues on Underlying Events
Fit : Expo+Linear FunctionsFrom 20 GeV to 120 GeV.
After correction, fluctuationis at the level of 3-5% whichis negligible compared toother systematics (~32%).
Default Sherpa sample is w/o UE. Erik generated ~2M events w/ UE. Because some jobs are crashed and slow?, Here trying to get Scale Factor here.
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Finalizing Trigger Rateas a function of ATLFAST Pt
1KHz (w/ FTK)
100Hz (w/o FTK)
30 50
So new working points : - 30 GeV (w/ FTK) and 50 GeV(w/o FTK).OLD setting : - 40 GeV (w/ FTK) and 70 GeV (w/o FTK)
-> All studies had to be redone !
* This is what we get withour current best knowledge.
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Based on LVL1 8x8 Calorimeter Parameterization
UE scale factor
1KHz (w/ FTK)
200Hz (w/o FTK)
25 35
@LVL1,w/ FTK (1KHz) : 25 GeVThen btagging @LVL2
w/o FTK (200Hz) : 35 GeVThen Jet Pt>50-60 @LVL2
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Summary of Trigger Rates & Threshold4Jet Trigger Rates 1KHz (LVL1 Max) 200Hz (LVL1 TDR) 100Hz (LVL2)
Atlfast Pt Thresh. > 30 GeV > 45 GeV > 50 GeV
8x8 Calo. Cluster E > 25 GeV (50% effi. to 30 GeV jet)
> 35 GeV (50% effi. to 45 GeV jet)
-
LVL1 Calo vs Atlfast Pt Correspondence * For Atlfast Jets, Assuming LVL2 Jet =~ Atlfast Jet
We need LVL2 reductionrate of 10 by either> Btagging (wFTK)> Raising Pt thresh (w/oFTK)
Is it possible (by FTK) ?Need mistag rate.(next page.)
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Issues on LVL2 ReductionThe reduction rate depends on trigger strategy :i.e. btagging is applied for means (1) Only Leading jets. (e.g. 4b for 4 leading jets) OLD(2) Any fiducial jets (eta<2.5) NEW
(1) Updated to (2)Not straightforward like linear behavior.
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LVL2 Reduction (Cont.)> It depends on the number of fiducial jets and real b quark contents.> Pythia and Sherpa are not much different. But it seems PYTHIA gives lower reductioni.e. it has either more fiducial Jets or/and more real b quarks.
With FTK btagging at LVL2,We need a reduction factorof >10 in order to keep Jet Pt threshold.
So the following conditionwould be enough :> 2tag if Ru > 10 (10% mistag)> 3tag if Ru > 4 (25% mistag)> 4tag for any Ru (>2)
better
Working point in this talk.
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Let’s Look at Signal Process
(each sample was generated with Atlfast simulation)
Coupling to up-typeis enhanced at low tan, so decay into ttbecomes large.
> bb decay : ~85-90% if tan >20
MA(GeV)
150 200 250 300 350 400 500 600 700 800 900
No Pt cut
Pt > 10
610
177
212
69.5
87.9
31.5
42.1
16.0
21.9
8.66
12.1
5.00
4.30
1.89
1.74
0.81
0.81
0.38
0.40
0.19
0.21
0.10
Cross section BR (pb)
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Signal Gain @ Trigger Level
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Signal Gain @ Trigger Level (Cont.)
Still expected N of background is ~1.5x10^9. So for the analysis, we have to optimize selection criteria.
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What if Trigger Rate is x3 higher ?If Trigger (Background) rate is x3 higher, Thresholds have to be
raised accordingly to keep LVL1 rate(1KHz) and LVL2 rate(100Hz).-> This is good study for uncertain QCD bkg & higher luminosity (10^34).
We lose signal acceptance, but relative improvement looks even powerful.
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(Offline) Optimization based onw/ and w/o FTK Conditions
> Requiring btag for “leading 3/4jets” for 3/4btags.> 1st,2nd ,3rd jet thresholds are optimized for different MA separately. > 4btag is more powerful than 3btag.
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(Offline) Optimization based onw/ & w/o FTK Conditions
Now results are not so good as before (which is more or less same asright plot (x3 bkg).). But I think that the most important thing is that even if the background rate is much higher due to high lum or MC miscalculation (in this case, x1 or x3) , FTK can provide almost same sensitivity ! But without FTK, very weak against higher background (compare dotted line.)
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Plan> Again, need inputs of realistic btagging efficiency and mistag rate to conclude. (Now @LVL2, 2tag with effb=50%, Ru=10 is required in order to reduce the rate by 10 (1KHz->100Hz).)
> Missing Pieces : - Complete & Summarize Multi-Threshold Study. - Dijet Mass Distribution
> Document it !
> FTK Simulation ?