31/5/2002 1

trigger optimization in CMS Tracker

Giuseppe BagliesiOn behalf of tracking group

Workshop on B/tau Physics at LHC Helsinki, May 30 - June 1, 2002

31/5/2002 G. Bagliesi – bTau workshop – Helsinki 30/5–

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Outline

HLT Pxl and Tk results with 3+2 and

2+1 pixel layout. CPU performances for Pxl and Tk Charged Higgs with Tracker

Off Line Tau tagging:

Preliminary studies on mass reconstruction

31/5/2002 G. Bagliesi – bTau workshop – Helsinki 30/5–

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High Level Trigger

Low luminosity: 2x1033 cm-2 sec-1

ORCA 4_5_4, CMSIM 120 Reading the DB with ORCA_5_3_4

gg (bb) A/H(200,500) (bb) 2 jets+X Final Goal is to achive a rejection factor ~ 1000 after L1

gb t H jet + 3Jets Final Goal is to achieve a rejection factor

30 after L1 and Missing ET cut.

PRELIMINARY RESULTS! High Luminosity: 1034 cm-2 sec-1

ORCA 6_1_0

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A. Nikitenko

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Isolation Algorithms

Signal vertex identified by:Pxl: leading track (PT>3GeV)Trk: best signal vertex candidate from pixel reconstruction.

signal vertex

leading track

jet

axi

s

jet

mat

chin

g c

one

R =

0

.1

signal cone

reg T

k cone

isolation

cone

Pxl: use pixel lines (i.e. tracks reconstructed only with pixel layers).Trk: use regional tracker reconstruction.

Both algorithms count numberof tracks inside signal (NSIG) cone and isolation cone (NISO).Events is accepted if leading trackexists and NSIG = NISO

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A. Nikitenko

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A. Nikitenko

31/5/2002 G. Bagliesi – bTau workshop – Helsinki 30/5–

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ORCA 6_1_0: Pixel isolation (I)H(500GeV) -> 2->jets

first jet is OK, small drop in efficiency due to more pxl. ineff. put in orca6. Second jet is OK for low lumi. Why it’s so bad for high lumi ? it’s due to way of finding 2-nd jet at Lvl- 2.

Sasha is tuning the L2 cuts for high Lumi

A. Nikitenko

31/5/2002 G. Bagliesi – bTau workshop – Helsinki 30/5–

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ORCA_6_1_0: pixel isolation (II)QCD background (PT: 50-80 GeV)

degradation of the rejection for qcd background due to the same reasons as for the signal

A. Nikitenko

31/5/2002 G. Bagliesi – bTau workshop – Helsinki 30/5–

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A. Nikitenko

31/5/2002 G. Bagliesi – bTau workshop – Helsinki 30/5–

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A. Nikitenko

31/5/2002 G. Bagliesi – bTau workshop – Helsinki 30/5–

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A. Nikitenko

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H -> HLT with full track

reconstruction A “must”: decrease CPU time…

First approach: Reconstruct tracks only around a region of

interest: regional tracking with a DetUnit filter Second approach:

seed selection in the region of interest Conditional Track Finder: stop trajectory

builder @ 6 hits Selection much faster than with regional tracking, but

loose ~5% signal efficiency and decrease bkg rejection of ~ 10 %

Next approach (in progress…) NewSeedGenerator “regional”

Optimization of the ROI… Fast (optimized) track finder (ORCA_6_1_1)

31/5/2002 G. Bagliesi – bTau workshop – Helsinki 30/5–

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DetUnit FilterDefinition of the ROI

DetUnit FilterDefinition of the ROI

layer n+1

layer n

DetUnit

DetUnit

DetUnit shape mapped by severalmarkers

If at least one marker is inside the cone the DetUnit is used

cone

CMS IN-2001/045

•A similar approach should be used for the regional seeding

31/5/2002 G. Bagliesi – bTau workshop – Helsinki 30/5–

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H(500GeV) -> 2->jets with tracker (ORCA_6_1_0) Comparison with Calo+Pxl (Low Lumi)

Similar Performances

31/5/2002 G. Bagliesi – bTau workshop – Helsinki 30/5–

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H(500GeV) -> 2->jets with tracker (ORCA_6_1_0) Comparison with Calo+Pxl (High Lumi)

Similar Performances

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H 2 2 Jets Selection with Tracker:performances (low luminosity) (ORCA_5)Full/Staged Pixel scenario comparison

3+2 2+1

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How to reduce tracking timein the isolation algorithm

RM=0.1

RSIG=0.065

RISO=0.45

RREG = 0.45

Jet

LT

Reconstruct tracks inside RM only

Find LT: If LT doesn’t exists stop

everything If LT exists apply isolation on rec

Tk, if it is not isolated stop everything

If event is isolated go on reconstructing also tracks inside region between RM and RREG

Apply isolation to all tracks. Depending on bkg sample and

pixel staged scenario a CPU time reduction varying from 20% to 40% is obtained

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Track reconstruction timeLow luminosity (ORCA_5)

Tracker Reconstruction steps (for single jet) :Time (sec) 3+2/2+1 (1 GHz cpu)

Bkg mH 200 mH 500

Pxl Reco 0.070 0.064 0.060

Trk Reco 1st Jet 0.125 0.056 0.050

Isolation for 1st jet

<0.005 <0.005 <0.005

Total Time 0.200/0.216 0.125/0.136 0.115/0.126

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H+j Selection with Tracker (I)

Low luminosity: 2x1033 cm-2 sec-1

3+2 pixels scenario (preliminary 2+1) Higgs mass = 200, 400 GeV/c2

L1 Calo = 1 -jet, ET > 80 GeV L2 = Missing ET (MET) + L2 Tk:

MET > 80 GeV L2 Tk: isolation + hard ptcut on leading track

Final Goal is a bkg rejection 30 after MET cut.

Preliminary results at 1034 cm-2 sec-1

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MET and isolation cut correlation

Missing ET cut and L2Tk selection are almost uncorrelated

To increase statistics no MET cut has been applied on plots.

QCD background H+->

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H+/- -> ->jet with tracker (ORCA_6_1_0)

Ntrk=1,3

NO MET cut, Low Lumi

ORCA_5best result

S. Gennai

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H+j Selection with Tracker (III)3+2 Pxl and 2+1 Pxl comparison

(ORCA_5)

RM=0.1, RS=0.065, RI=0.4

PTLTCUT = 1. – 25. GeV

RM=0.1, RS=0.065, RI=0.4

PTLTCUT = 1. – 25. GeV

Staged Scenario

2+13+2

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H+/- -> ->jet with tracker (ORCA_6_1_0)

NO MET cut, High Lumi

Ntrk=1,3

S. Gennai

Performances similar to Low Lumi

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Off Line tau tagging

Preliminary studies on reconstructed tau mass in hadronic tau decays

To do: ORCA_6_1_0 (in progress…) Combination with vertex

reconstruction reconstruction

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Preliminary results on tau mass tag

•ORCA_6_1_0

•events passing LVL1 selection

•Arbitrary units (normalization on number of entries)

•At least one (or three) tracks in the reconstruction cone

• 0 are taken from MC truth. •R<0.4 around the jet direction•Et > 1 GeV

S. Dutta

Ntk>0

Ntk>2

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Conclusions

H->->jets 45% (30% with ORCA_6???) efficiency with ~2x103 QCD

rejection is achievable at L2 (both with Calo + Pxl and Trk + Pxl) 3+2 Vs 2+1 scenario:

Pxl can get the same efficiency and bkg rejection using also L2Calo Trk has decrease in efficiency of ~ 10% (@ the same Bkg Rate)

Charged Higgs (L2TK isolation) Signal Eff. ~ 50 % with Bkg Rej ~ 30

Timing (low luminosity): Pxl can identify taus in less 50 msec Tk can identify single tau in ~192 msec (Single with hard PT cut)

Work in progress … High luminosity

Timing Performances

Off Line Tagging (mass + vertex tag)