The Silicon Track Trigger The Silicon Track Trigger (STT) at D(STT) at DØØ

Beauty 2005 in Assisi, June 2005Beauty 2005 in Assisi, June 2005

Sascha Caronfor the DØ collaboration

Tag beauty

fast …

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The Silicon Track Trigger at DThe Silicon Track Trigger at DØØ

OUTLINEOUTLINE

- D0 detector- D0 trigger- What is the STT?- dataflow- clustering and tracking- B identification- Performance- Summary

Sascha CaronSascha Caron

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The Silicon Track Trigger at DThe Silicon Track Trigger at DØØ

Sascha CaronSascha Caron

D0 in Run IID0 in Run II

The Silicon Track The Silicon Track Trigger is based Trigger is based on informationon informationof the :of the :

Silicon Microstrip Silicon Microstrip TrackerTracker

Central Fiber Central Fiber Tracker Tracker

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The Silicon Track Trigger at DThe Silicon Track Trigger at DØØ

Sascha CaronSascha Caron

D0 in Run IID0 in Run II

The Silicon Track The Silicon Track Trigger is based Trigger is based on informationon informationof the :of the :

Silicon Microstrip Silicon Microstrip TrackerTracker

Central Fiber Central Fiber TrackerTracker

o 50 50 μμm pitch strips (parallel to beam)m pitch strips (parallel to beam)o 800000 readout channels800000 readout channelso Only axial strips used for STT tracksOnly axial strips used for STT tracks

o Scintillating fibersScintillating fiberso Coverage: |Rapidity| < 1.7Coverage: |Rapidity| < 1.7

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The Silicon Track Trigger at DThe Silicon Track Trigger at DØØ

Sascha CaronSascha Caron

Events forEvents for L=100 E30 cmL=100 E30 cm-2-2/s/s= about 8 pb= about 8 pb-1-1/day/day

1010

11

0.10.1

0.010.01

0.0010.001

Higgs->b bbarHiggs->b bbar

ZH-> bbvv, bH->bbb etc.ZH-> bbvv, bH->bbb etc.

Z-> b bbarZ-> b bbar

QCD EQCD ETT>30 GeV >30 GeV dijet productiondijet production

b-jets Eb-jets ETT>30 GeV>30 GeV

0.00010.0001

Events Events per per

secondsecond

Find b-events Find b-events early to keep early to keep high efficiencyhigh efficiency

at an acceptableat an acceptableraterate

Find b-events Find b-events early to keep early to keep high efficiencyhigh efficiency

at an acceptableat an acceptableraterate

Aim: High EAim: High ETT

Z->bb, HZ->bbvv, Z->bb, HZ->bbvv, H->bb, etc.H->bb, etc.Hopefully B Hopefully B

physicsphysics

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The Silicon Track Trigger at DThe Silicon Track Trigger at DØØ

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Principal IdeaPrincipal Idea

B B decay length is mm

decay length is mm

Impact parameterImpact parameter(2d in x-y plane)(2d in x-y plane)

B decay productsB decay products

o Silicon Improved Tracks withSilicon Improved Tracks with 2d impact parameter2d impact parameter

o Select events with large impact parameter tracksSelect events with large impact parameter tracks

Interaction point Interaction point is mean beam spotis mean beam spot

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The Silicon Track Trigger at DThe Silicon Track Trigger at DØØ

Sascha CaronSascha Caron

L1 TriggerL1 Trigger decision timedecision time

about 4 about 4 μμss

(1500) (1500) 5000 Hz5000 Hz

(700)(700)1000Hz1000Hz 50 Hz50 Hz2.5MHz2.5MHz L2 TriggerL2 Trigger

decision timedecision timeabout 200 about 200 μμss

L3 TriggerL3 Trigger decision timedecision timeabout 50 msabout 50 ms

Trigger SystemTrigger System

p p bunchp p bunch

crossing crossing frequencyfrequency

¯̄

o Hardware basedHardware basedo CTT tracks, CTT tracks, calorimeter towers, calorimeter towers, muonsmuons

o Hardware/Software Hardware/Software o simple jets, electrons, simple jets, electrons, muons, tausmuons, tauso Silicon Microvertex Silicon Microvertex improved tracks (STT)improved tracks (STT)o global processor to global processor to combine informationcombine information (e.g. STT tracks for Bid)(e.g. STT tracks for Bid)

o Software basedSoftware basedo partial event partial event reconstructionreconstruction

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The Silicon Track Trigger at DThe Silicon Track Trigger at DØØ

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SiliconSiliconMicro Micro

DetectorDetector

CentralCentralFiberFiber

TrackerTracker

L2L2STTSTT

L1L1CTTCTT

L2L2CTTCTT

L2L2GlobalGlobal

otherotherL2 pre- L2 pre-

processorsprocessors

DetectorDetector Level 1Level 1 Level 2Level 2Level 1Level 1DetectorDetector

Data flow chart L2 tracksData flow chart L2 tracks

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The Silicon Track Trigger at DThe Silicon Track Trigger at DØØ

Sascha CaronSascha Caron

How is the How is the tracking improved?tracking improved?

o Tracks found at L1 with the Central Fiber Tracks found at L1 with the Central Fiber Tracker are used to define roads into the Tracker are used to define roads into the Silicon Silicon

o Silicon hits are clusteredSilicon hits are clustered

o Track is re-fit within the roadTrack is re-fit within the road

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The Silicon Track Trigger at DThe Silicon Track Trigger at DØØ

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Silicon Track Trigger cardsSilicon Track Trigger cards

Road data toRoad data toFiber Road CardFiber Road Card

SMT data to SMT data to 9 Silicon Trigger9 Silicon Trigger

CardsCards

Fitting done Fitting done in Track Fit Card in Track Fit Card

L2CTTL2CTT

Done in parallel for each of the 12 sectors

2 sectors in 1 crate-> 6 Crates with1 Fiber Road Card9 Silicon Trigger Cards2 Track Fit Cards

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The Silicon Track Trigger at DThe Silicon Track Trigger at DØØ

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Silicon Track Trigger cardsSilicon Track Trigger cards Road data toRoad data toFiber Road CardFiber Road Card

- Receives and distributes L1 - Receives and distributes L1 trackstracks- Communicates with TriggerCommunicates with Trigger frameworkframework

SMT data to SMT data to Silicon TriggerSilicon Trigger

CardsCards

- Perform clustering and cluster-road matching

- Clusters SMT hits + pedestal correction

- Axial clusters are matched to the roads

Fitting done Fitting done in Track Fit Card in Track Fit Card

- receives road and axial clusters- receives road and axial clusters- convert to physics coordinates via LUTconvert to physics coordinates via LUT- perform track fit perform track fit φφ(r)= b/r+kr+(r)= b/r+kr+φφ00 - beam spot correctionbeam spot correction- output tracks to L2CTToutput tracks to L2CTT

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The Silicon Track Trigger at DThe Silicon Track Trigger at DØØ

Sascha CaronSascha Caron

Performance studies STT tracksPerformance studies STT tracks

Impact Parameter resolution Impact Parameter resolution Correlation to RECO Correlation to RECO

ppTT(GeV)(GeV)

Res

olut

ion

in

Res

olut

ion

in

μμmm

PurityPurity

Including beam spot size 35 Including beam spot size 35 μμm m and 15 and 15 μμm SMT resolutionm SMT resolution

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The Silicon Track Trigger at DThe Silicon Track Trigger at DØØ

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- Fast, simple and efficient technique- Time needed is 2 operations per track and goes linear with the number of tracks -> about 1-5 μs- Degrades bad tracks without cutting them

Store 2d signal (b events) to background (light quarks) ratio into a lookup table

Defi ne “good tracks”

Loop over tracks i and derive the product R= ∏Ri

or use max(Ri)

Likelihood as a discriminator: L= R/ (R+1)

B B identification identification Signal to Signal to Background Background

ratioratio

b/db b/db

1.5 1.5 mmmm

RRii

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The Silicon Track Trigger at DThe Silicon Track Trigger at DØØ

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Performance studiesPerformance studies

Very well separation of signal and Very well separation of signal and background eventsbackground events

Large background reductionLarge background reductionwith L2 b-ID algorithmswith L2 b-ID algorithms

efficiency Z->bbefficiency Z->bbL2 B-id likelihoodL2 B-id likelihood

Red : Red : Simple CutSimple Cut

BlueBlue//GreenGreen: : B-idB-id

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The Silicon Track Trigger at DThe Silicon Track Trigger at DØØ

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First studiesFirst studiesusing datausing data

Max IP Significance Max IP Significance Likelihood Likelihood

L2 data well correlated with offline dataL2 data well correlated with offline data-> proof of b-id principle -> Much more studies on their way-> proof of b-id principle -> Much more studies on their way

Jet dataJet data Offline B-tagged Offline B-tagged

data data

Likelihood shifted toLikelihood shifted tohigher values duehigher values due

to e.g. min bias effectsto e.g. min bias effects

DDØØpreliminarypreliminary

Using MC pdfsUsing MC pdfs

DDØØpreliminarypreliminary

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The Silicon Track Trigger at DThe Silicon Track Trigger at DØØ

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SummarySummary

o The STT is operating routinely and smooth The STT is operating routinely and smooth o High Impact Parameter resolutionHigh Impact Parameter resolutiono Data is understoodData is understoodo Very fast L2 b-id is (almost) implemented Very fast L2 b-id is (almost) implemented o We expect a high potential forWe expect a high potential for Z->bb and Higgs physics now and at L=200E30cmZ->bb and Higgs physics now and at L=200E30cm-2-2/s/s

OutlookOutlook

o Implementation of new Layer 0 (r=22mm) into STT Implementation of new Layer 0 (r=22mm) into STT -> further increase in precision and stability -> further increase in precision and stability