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

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

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.

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.

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.

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.

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

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.)

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.

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.

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)

Signal Gain @ Trigger Level

Signal Gain @ Trigger Level (Cont.)

Still expected N of background is ~1.5x10^9. So for the analysis, we have to optimize selection criteria.

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.

(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.

(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.)

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 ?