HLT tau trigger with regional tracking

G. Bagliesi, S. Dutta, S. Gennai, G. Sguazzoni

TISB Pisa 12/10/01

G. Bagliesi, S. Dutta, S. Gennai, C. Schmidt, G. Sguazzoni – bTau 250901 2

Process studied

Low luminosity: Susy gg->(bb) A/H(200,500) -> (bb) -> 2 Jets+X

Main background is QCD (50<PThat170)

Pixel “staged” scenario study: 3 layers + 2 disk: “standard” 2 layers + 1 disk: “staged” (preliminary

results!)

ORCA 4_5_4, CMSIM 120But we are reading the DB with ORCA_5_1_2No pixel read-out inefficiency

1233 scm102 L

G. Bagliesi, S. Dutta, S. Gennai, C. Schmidt, G. Sguazzoni – bTau 250901 3

Data samples

N prod After L1

Rate (kHz)

Weight

QCD 50-80 150000

8268 2x1.34

0.476

QCD 80-120 38501 13493 2x1.18

0.420

QCD 120-170 50000 25878 2x0.29

0.103

bbH(200) ->

5000 4465

bbH(500) ->

5000 4729

1233 scm102 L

G. Bagliesi, S. Dutta, S. Gennai, C. Schmidt, G. Sguazzoni – bTau 250901 48 June 2001 BTau MiniWorkshop - G.Bagliesi, S.Dutta, S.Gennai, G.Sguazzoni 3

Overview of the trigger chainOverview of the trigger chain

L1(Calorimeter based) A.Nikitenko et al. CMS NOTE 2000/055 A.Nikitenko talk in this workshop

HighLevelTrigger L2 (Calorimeter based)

see L1 refs.

L3Pxl (Pixel detector based) D.Kotlinski et al. CMS NOTE 2001/017 D.Kotlinski talk in this workshop

L3Tk (note in preparation): regional tracking based

G. Bagliesi, S. Dutta, S. Gennai, C. Schmidt, G. Sguazzoni – bTau 250901 5

No L2 applied on 1st jet: more flexibililityNo L2 applied on 1st jet: more flexibilility

H/A

1st jet

2nd jet

1st jet

trig

ger

chain

2n

d jet

trig

ger

chain

L3Tk (iso, #tk)

L1(iso)

.AND.L1

(iso)

L2(iso)

calo

calo

L3Tk(iso)p

ixel

tracker

calo

G. Bagliesi, S. Dutta, S. Gennai, C. Schmidt, G. Sguazzoni – bTau 250901 68 June 2001 BTau MiniWorkshop - G.Bagliesi, S.Dutta, S.Gennai, G.Sguazzoni 18

Tk isolation cutTk isolation cut

The leading track ofisolation cone should be inthe jet matching cone

All tracks within theisolation cone should beconcentrated in the signalcone

signal vertex

Similar to the L3Pxl

The regional tracking coneembeds all others cones

leading tracksignal cone

G. Bagliesi, S. Dutta, S. Gennai, C. Schmidt, G. Sguazzoni – bTau 250901 9

What is new?Look for a Pixel leading track in the jet matching cone (Rm=0.4, it was 0.1 before)If no pixel leading track is found, take the most probable signal vertex ~10% of good signal events recovered ~3% change in bkg: more probable to find a

leading track since more tracks are around…

Ptcut on leading track = 1 GeV (it was 3 GeV)

Reconstruct second tau jet (if any) pointing to the same signal vertex

G. Bagliesi, S. Dutta, S. Gennai, C. Schmidt, G. Sguazzoni – bTau 250901 10

Pt distribution from pythia

11

L2Tk jet tagging algorithm

“Good Track” definition PT>1 Gev |Z0-Zsignal|<0.2

Jet tau tagging: look for a fully reconstructed leading track with

PT>1 GeV (or calculate baricenter of tracks inside the cone) Apply isolation cut (already described)

Scan on Rs, Ri to find optimal parameters Rs=0.04, 0.06, 0.08, 0.1 Ri=0.4, 0.35, 0.3, 0.25, 0.2

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L2Tk on first and second jet

Rs

Ri

First jet only First and second jet

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L2Calo + L3Tk isolation

With both Calo and Tk selection we can achieve the desired rejection

factor.

14

Summary PlotUsing:

• Rs = 0.04

• Ri = 0.3

And L2Calo on first jet we have:

• Bkg Rej = 10-3

• Sig Eff.

• MH500 = 45%

• MH200 = 35%

15

Staged pixel scenario

•2 barrel layers•1 forward disk•Comments:

•Track finder not optimized at seed level

•Preliminary!

10% signal efficiency degradation expected

Staged

Not staged

16

TauTkTagging.cc TauTkTagging(float eta, float phi, G3EventProxy

*ev)methods>: Vector<RecTrack> regionalTk()

Return a vector of reconstructed tracks inside jet cone and from the same primary vertex.

Bool isTau() Return true if the jet pass Tk isolation criteria.

Committed under bTauAnalysis/TauTaggingAlgorithms (works with ORCA_5_1_2)

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Conclusions

Good signal efficiency ~40% (>30%) with ~103 background rejection factor is achievable using both jets for 500 Gev/c2 (200 Gev/c2) Higgs mass“Tau class” committed and working.To do: Improve speed: conditional track finding

implementation and evaluation Study the SimTracks to tune better the algorithm Tau Tagging: mass, vertex, I.P.