Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 CMS Inner Tracking

Marcello Mannelli CMS Inner TrackingCMS Inner Tracking LHC Symposium May 2003

CMS Inner TrackingCMS Inner Tracking


High Luminosity Physics at the LHCHigh Luminosity Physics at the LHC

““Golden Channel”Golden Channel”

Tracker Requirements:Tracker Requirements:

Efficient & robust Pattern Recognition algorithmEfficient & robust Pattern Recognition algorithm

Fine granularity to resolve nearby tracksFine granularity to resolve nearby tracksFast response time to resolve bunch crossingsFast response time to resolve bunch crossings

Ability to reconstruct narrow heavy objectAbility to reconstruct narrow heavy object

1~2% Pt resolution at ~ 100GeV1~2% Pt resolution at ~ 100GeV

Ability to tag b/Ability to tag b/ through secondary vertex through secondary vertex

Good impact parameter resolutionGood impact parameter resolution

This Review: HLT, including b & This Review: HLT, including b & jet tags jet tags

pp & High luminosity => “mess”pp & High luminosity => “mess”


The CMS Pixel Vertex detector:The CMS Pixel Vertex detector:Silicon strips have become pixelsSilicon strips have become pixels

The region below 20cm is instrumentedThe region below 20cm is instrumentedwith Silicon Pixel Vertex systemswith Silicon Pixel Vertex systems

The Pixel area is driven by FE chipThe Pixel area is driven by FE chipThe shape is optimized for resolutionThe shape is optimized for resolution

CMS pixel ~ 150 * 150 CMS pixel ~ 150 * 150 mm22

With this cell size, and exploitingWith this cell size, and exploitingthe large Lorentz anglethe large Lorentz angle

We obtain IPWe obtain IPtrans. trans. resolution ~ 20 resolution ~ 20 mmfor tracks with Pfor tracks with Pt t ~ 10GeV~ 10GeV

93 cm93 cm

30 cm30 cm

4 104 1077 pixels pixels

Shaping time ~ 25nsShaping time ~ 25ns

With this cell size occupancy is ~ 10With this cell size occupancy is ~ 10-4-4

This makes Pixel seeding the fastestThis makes Pixel seeding the fastestStarting point for track reconstructionStarting point for track reconstruction

DespiteDespite the extremely high track density the extremely high track density


From strip Vertex to strip TrackingFrom strip Vertex to strip Tracking

Single-sided, AC coupled, polysilicon biased sensors have Single-sided, AC coupled, polysilicon biased sensors have become a mature technologybecome a mature technology

Costs have decreased, and large scale production is now possibleCosts have decreased, and large scale production is now possible

High level of expertise for FE IC design and system aspects of High level of expertise for FE IC design and system aspects of O(10O(105) 5) channelschannels

Move to detectors with a high level of independent tracking Move to detectors with a high level of independent tracking capabilitycapability

A few mA few m22 : : CDF – D0CDF – D0

Several * 10Several * 1011mm22 : : ATLASATLAS

A couple * 10A couple * 1022 m m2 2 :: CMSCMS


The CMS TrackerThe CMS Tracker::220m220m22 of silicon strip sensors of silicon strip sensors

5.4 m

Outer Barrel –TOB-

Inner Barrel –TIB-

End cap –TEC-Pixel

2,4

m

volume 24.4 m3

running temperature – 10 0Cdry atmosphere for YEARS!

Inner Disks –TID-


SST Module level ComponentsSST Module level Components

9’648’128 strips 9’648’128 strips channelschannels

75’376 APV chips75’376 APV chips

6’136 Thin sensors6’136 Thin sensors18’192 Thick sensors18’192 Thick sensors

440 m440 m22 of silicon wafers of silicon wafers 210 m210 m22 of silicon sensors of silicon sensors

3’112 + 2*1’512 Thin 3’112 + 2*1’512 Thin modulesmodules

5’496 + 2*1’800 Thick 5’496 + 2*1’800 Thick modulesmodules

ss ds=b-to-bss ds=b-to-b

~17’000 modules~17’000 modules

~25’000’000 Bonds~25’000’000 Bonds

FE FE hybrid hybrid with FE with FE ASICSASICS

Pitch Pitch adapteradapter

Silicon Silicon sensorssensors

CF frameCF frame

Large scale 6” industrialLarge scale 6” industrialsensor productionsensor production

Automated moduleAutomated moduleassemblyassembly

Reliable, High YieldReliable, High YieldIndustrial IC processIndustrial IC process

State of the artState of the artBonding machinesBonding machines


The radiation hard P-on-N strip detectorThe radiation hard P-on-N strip detector

Single-Sided Lithographic ProcessingSingle-Sided Lithographic Processing( AC, Poly-Si biasing )( AC, Poly-Si biasing )

N Bulk

N+ Implants

P+ implants

Al Strips

“P” Bulk

N+ Implants

P+ implants

+++++

----- +++++

-----

- - - - -+++++

Surface damage

Radiation hardness “recipe”Radiation hardness “recipe”

P-on-N sensors work after bulk type inversion,P-on-N sensors work after bulk type inversion,Provided they are Provided they are biased well above depletionbiased well above depletion

Match sensor resistivity & thickness to fluenceMatch sensor resistivity & thickness to fluenceTo optimize S/N over the full life-timeTo optimize S/N over the full life-time

Follow simple design rules for guard & strip geometryFollow simple design rules for guard & strip geometry

Use Al layer as field plate to remove high fieldUse Al layer as field plate to remove high field@edges from Si bulk to Oxide (much higher V@edges from Si bulk to Oxide (much higher Vbreakbreak))

Strip width/pitch ~ 0.25: reduce CStrip width/pitch ~ 0.25: reduce Ctottot maintain maintainStable high bias voltage operationStable high bias voltage operation

Take care with process: especially implants…Take care with process: especially implants…

Surface radiation damage canSurface radiation damage canincrease strip capacitance & noiseincrease strip capacitance & noise

Use <100> crystal instead of <111>Use <100> crystal instead of <111>


Silicon Strip Sensor PropertiesSilicon Strip Sensor Properties

Strip capacitance ~ 1.2pF/cm for w/p = 0.25Strip capacitance ~ 1.2pF/cm for w/p = 0.25Independent of pitch and thicknessIndependent of pitch and thickness

Use Use m thick Si for R < 60cm, Stripm thick Si for R < 60cm, Strip ~ 10cm~ 10cm

Use Use m thick Si for R > 60cm, Stripm thick Si for R > 60cm, Strip ~ 20cm~ 20cm

Expected S/N after irradiationExpected S/N after irradiation

S/N ~ 13 for thin sensors, short stripsS/N ~ 13 for thin sensors, short stripsS/N ~ 15 for thick sensors, long stripsS/N ~ 15 for thick sensors, long strips

Insensitive to irradiationInsensitive to irradiationfor <100> crystal latticefor <100> crystal lattice


The CMS Silicon Strip Tracker: from 4” to 6”The CMS Silicon Strip Tracker: from 4” to 6”

The CMS SST exploits 6” technology:The CMS SST exploits 6” technology:

Useful surface/wafer ~ 2.5 * that of 4” wafersUseful surface/wafer ~ 2.5 * that of 4” wafers

Large scale high quality sensor production in modernLarge scale high quality sensor production in modernIndustrial lines available from more than one vendor:Industrial lines available from more than one vendor:

Hamamatsu produces the “thin” 320Hamamatsu produces the “thin” 320 sensors; sensors;ST-Microelectronics the “thick” 500ST-Microelectronics the “thick” 500 sensors sensors

Production is well underway:Production is well underway:

Hamamatsu: excellent quality, some concerns regardingHamamatsu: excellent quality, some concerns regardingSelection of sufficiently low resistivity raw materialSelection of sufficiently low resistivity raw material

ST: production quality also good, problems dueST: production quality also good, problems dueTo inappropriate manipulation of sensors duringTo inappropriate manipulation of sensors during

Testing are being addressedTesting are being addressed


Front-End HybridsFront-End Hybrids

This has proven to be a major challenge, and has defined theThis has proven to be a major challenge, and has defined theCritical path for module assembly. We have finally converged Critical path for module assembly. We have finally converged on:on:

• 4 layer Kapton flex circuit:4 layer Kapton flex circuit:• high resolution multi-layer Kapton circuits now available industrially in large high resolution multi-layer Kapton circuits now available industrially in large volumesvolumes•““seamless” integration of flexible pig-tailseamless” integration of flexible pig-tail

• Laminated onto a ceramic substrateLaminated onto a ceramic substrate• need rigidity for bonding chips to hybridneed rigidity for bonding chips to hybrid

•ceramic chosen since adequate thermally and mechanically (flatness!) ceramic chosen since adequate thermally and mechanically (flatness!) and cheapand cheap

• provides support for pitch adapterprovides support for pitch adapter• can fully bond the hybrid to pitch-adapter assembly before gluing on can fully bond the hybrid to pitch-adapter assembly before gluing on module framemodule frame

Pre-series production end of 2002 => Design fine-tuned for efficient lamination Pre-series production end of 2002 => Design fine-tuned for efficient lamination and componentand componentassembly and wire-bonding. Hybrid production now ramping up, module assembly assembly and wire-bonding. Hybrid production now ramping up, module assembly followingfollowing


The Gantry in actionThe Gantry in actionAssembly of 3 TOB ModulesAssembly of 3 TOB Modules

Assemblyplatform

Carbonfiber

frames

Hybrids

Silicon sensors

Tool rack

Glue dispensing syringes

Sensor pick up tool

Hybridpick up tool

Vacuum system


Placement accuracy and reproducibilityPlacement accuracy and reproducibilitywith automatic pattern recognitionwith automatic pattern recognition

Image found: placeImage found: place

Sensor pair preciselySensor pair precisely

““Gantry see, Gantry do”Gantry see, Gantry do”

The gantry system localizes The gantry system localizes automatically the components to be automatically the components to be assembled by searching for a assembled by searching for a Marker with a cameraMarker with a camera

X

3 m

Sensors within a module areSensors within a module areplaced to better than 5placed to better than 5 and 2mr and 2mr

Relative to each otherRelative to each other

Miss-placements of up to 10Miss-placements of up to 10do not significantly degrade thedo not significantly degrade the

Ultimate muon Pt resolutionUltimate muon Pt resolutioneven if not corrected for in track reconstructioneven if not corrected for in track reconstruction


S/N performance in System TestsS/N performance in System Tests

S/N ~ 25(20% higher than rays)

If muons (@ 500 m) = 40000 electronsnoise (@ deco) = 1600 electrons

identical to predictions.


Basic design and performance considerationsBasic design and performance considerationsfor the CMS Trackerfor the CMS Tracker

To set the scale for the momentum measurement, recall To set the scale for the momentum measurement, recall that:that:

The CMS B Field = 4T and the TK Radius ~ 110 cm result The CMS B Field = 4T and the TK Radius ~ 110 cm result in:in:

1.9mm sagitta for 100 GeV P1.9mm sagitta for 100 GeV Ptt tracks tracks

(190(190 sagitta for 1 TeV P sagitta for 1 TeV Ptt tracks) tracks)

To set the scale for speed and granularity, recall that:To set the scale for speed and granularity, recall that:

At high luminosity expect ~ 20 min. bias events every 25nsAt high luminosity expect ~ 20 min. bias events every 25ns=> a very high charged particle flux (modified the B field)=> a very high charged particle flux (modified the B field)

R = 10cm 25cm 60cmR = 10cm 25cm 60cm

NNchch/(cm/(cm22*25ns) = 1.0 0.10 0.01*25ns) = 1.0 0.10 0.01


The CMS Tracking StrategyThe CMS Tracking Strategy

Rely on “few” measurement layers,Rely on “few” measurement layers,each able to provideeach able to provide

robust (clean) and precise coordinate determinationrobust (clean) and precise coordinate determination

2 to 3 Silicon Pixel, and 10 to 14 Silicon Strip Measurement Layers2 to 3 Silicon Pixel, and 10 to 14 Silicon Strip Measurement Layers

6 layers6 layersTOBTOB

4 layers4 layersTIBTIB

3 disks TID3 disks TID 9 disks TEC9 disks TEC

R-phi (Z-phi) onlyR-phi (Z-phi) onlymeasurement layersmeasurement layers

R-phi (Z-phi) & StereoR-phi (Z-phi) & Stereomeasurement layersmeasurement layers

Radius ~ 110cm, Length ~ 270cmRadius ~ 110cm, Length ~ 270cm ~1.7~1.7

~2.4~2.4


Design considerations for CMS SST:Design considerations for CMS SST:Cell size & strip pitchCell size & strip pitch

Efficient & clean track reconstruction isEfficient & clean track reconstruction isensured provided ensured provided occupancy below few %occupancy below few %

At small radii need cell size < 1cmAt small radii need cell size < 1cm22

and fast (~25ns) shaping timeand fast (~25ns) shaping timeThis condition is relaxed at large radiiThis condition is relaxed at large radii

PPtt/ P/ Pt t ~ 0.1*P~ 0.1*Ptt (P (Ptt in TeV) in TeV)allows to reconstruct Z to allows to reconstruct Z to with with

mmZZ < 2GeV up to P < 2GeV up to Ptt ~ 500GeV ~ 500GeV

Twelve layers with (pitch/ Twelve layers with (pitch/ 12) spatial resolution 12) spatial resolutionand 110cm radius give a momentum resolution ofand 110cm radius give a momentum resolution of

Tev

p

B

T

L

m

m

pitch

p

p

1

41.1

10012.0

121

A typical pitch of order A typical pitch of order mmis required in the phi coordinateis required in the phi coordinate

To achieve the required resolutionTo achieve the required resolution

Strip length ranges Strip length ranges fromfrom 10 cm10 cm in the inner layers in the inner layers to 20 cmto 20 cm in the outer layers. in the outer layers.

Pitch ranges Pitch ranges from 80from 80mm in the inner layers to near in the inner layers to near 200200mm in the outer layers in the outer layers


Robust and clean hitsRobust and clean hits

Hit contamination is ~ 4% in the first Silicon Strip layerHit contamination is ~ 4% in the first Silicon Strip layer

Less than ~ 2% elsewhereLess than ~ 2% elsewhere

4%4%

2%2%


Partial Track reconstructionPartial Track reconstruction

Good track parameter resolutionGood track parameter resolution

already with 4 or more hitsalready with 4 or more hits


Robust Pattern RecognitionRobust Pattern Recognition

Well defined track parameters with 4 or more hitsWell defined track parameters with 4 or more hits

=> Small uncertainties on the predicted track state=> Small uncertainties on the predicted track state

1mm1mm

200200

1mm1mm

400400



~ 15-20% of track candidates~ 15-20% of track candidatesAre matched to a spurious hitAre matched to a spurious hit

~ 1% of track candidates~ 1% of track candidatesAre matched to a spurious hitAre matched to a spurious hit



Even in the most crowded situations,<10% of track candidatesEven in the most crowded situations,<10% of track candidatesextrapolated from Barrel Si Strip layer 1 are matched to a spurious hitextrapolated from Barrel Si Strip layer 1 are matched to a spurious hit


Track reconstructionTrack reconstruction


Track reconstruction efficiency in jetsTrack reconstruction efficiency in jets

Efficiency for particles in a 0.4 cone around jet axisEfficiency for particles in a 0.4 cone around jet axis

No significant degradation compared to single pionsNo significant degradation compared to single pions

Loss of efficiency is dominated by hadronic interactionsLoss of efficiency is dominated by hadronic interactions

in Tracker materialin Tracker material

95%95% 95%95%


Impact Parameter resolutionImpact Parameter resolution

For 10 GeV Pt tracks, For 10 GeV Pt tracks, (d(d00) <30) <30 for for <1.5; degrading to ~ 40<1.5; degrading to ~ 40 for for =2.4=2.4

For 10 GeV Pt tracks, For 10 GeV Pt tracks, (Z(Z00) <50) <50 for for <1.5; degrading to ~150<1.5; degrading to ~150 for for =2.4=2.4


Pt Resolution For High Momentum MuonsPt Resolution For High Momentum Muons

The CMS Tracker provides ~ 1% Pt resolution over ~ 0.9 units of The CMS Tracker provides ~ 1% Pt resolution over ~ 0.9 units of ,,and 2% Pt resolution up to and 2% Pt resolution up to ~ 1.75, beyond which the lever arm is reduced ~ 1.75, beyond which the lever arm is reduced

Even at 100 GeV muons are significantly affected by multiple scattering:Even at 100 GeV muons are significantly affected by multiple scattering:a finer pitch, and higher channel counta finer pitch, and higher channel count

Would therefore yield only diminishing returns in improving the Pt resolutionWould therefore yield only diminishing returns in improving the Pt resolution


Alignment tools and strategyAlignment tools and strategy

Pattern recognition works Pattern recognition works efficiently and cleanly efficiently and cleanly

with misalignments of up to with misalignments of up to 1mm, for W->1mm, for W-> events at events at

2*102*103333

This is the essential startingThis is the essential startingPoint for alignment with tracksPoint for alignment with tracks

Tools implemented to introduce,Tools implemented to introduce,And account for, misalignmentsAnd account for, misalignments

Following the hierarchical organizationFollowing the hierarchical organizationOf the mechanical degrees of freedomOf the mechanical degrees of freedom

Inherent in the support structuresInherent in the support structures


High quality track reconstruction codeHigh quality track reconstruction code

Fully functional code released ~ January 2001Fully functional code released ~ January 2001Good efficiency and track qualityGood efficiency and track quality

Well designed modular architecture Well designed modular architecture Excellent framework for systematic optimizationExcellent framework for systematic optimization

Pixel Seeds

TrajectoryBuildingSmoothing

>80%

<5%

<10%

Timing analysis: 85% in Trajectory Timing analysis: 85% in Trajectory buildingbuilding

Dominated by search for compatible Dominated by search for compatible layerslayers

5 times faster layer search5 times faster layer search=> Overall 3 times faster => Overall 3 times faster

reconstruction (at least in the barrel)reconstruction (at least in the barrel)

Example of technical improvements:Example of technical improvements:Previous track propagator wasPrevious track propagator was

““good enough for government work”good enough for government work”

New track propagator ~ perfectNew track propagator ~ perfect


40 MHZ40 MHZ

50 KHz50 KHz

100 Hz100 Hz

4 DAQ slices in 20074 DAQ slices in 2007=> 50 KHZ into HLT, 100 Hz out=> 50 KHZ into HLT, 100 Hz out

The CMS Trigger and DAQ architectureThe CMS Trigger and DAQ architectureTwo level data reduction: Lvl-1 trigger & HLT filterTwo level data reduction: Lvl-1 trigger & HLT filter

On average ~300ms available for HLTOn average ~300ms available for HLTDecision on any given eventDecision on any given event

(Normalized to a 1GHz Pentium)(Normalized to a 1GHz Pentium)

Lvl-1 = “crude”Lvl-1 = “crude”granularity and Pt resolution:granularity and Pt resolution:

Rate dominated byRate dominated bymiss-measured jets & leptonsmiss-measured jets & leptons

HLT task: reduce rate by ~ 1000HLT task: reduce rate by ~ 1000Exploit much betterExploit much better

Granularity and Pt resolutionGranularity and Pt resolutionto correctly tag and retainto correctly tag and retain

only interesting physics eventsonly interesting physics events


Examples of Tracker @ HLT: tau taggingExamples of Tracker @ HLT: tau tagging

Regional TrackingRegional Tracking: Look only in: Look only inJet-track matching coneJet-track matching cone

Loose Primary Vertex associationLoose Primary Vertex association

Conditional TrackingConditional Tracking: Stop track as soon as: Stop track as soon asPixel seed found (PXL) / 6 hits found (Trk)Pixel seed found (PXL) / 6 hits found (Trk)

If Pt<1 GeV with high C.L.If Pt<1 GeV with high C.L.

Reject event if no “leading track” foundReject event if no “leading track” found

Regional TrackingRegional Tracking: Look only inside: Look only insideIsolation coneIsolation cone


Conditional TrackingConditional Tracking: Stop track as soon as: Stop track as soon asPixel seed found (PXL) / 6 hits found (Trk)Pixel seed found (PXL) / 6 hits found (Trk)


Reject event as soon as additional track foundReject event as soon as additional track found


Calo-PXL ACalo-PXL A00/H/H00->2->2->2->2jetsjets

Optimization of the Calo-PXL signal efficiency as a function of Optimization of the Calo-PXL signal efficiency as a function of the Calo Tau Trigger suppression factorthe Calo Tau Trigger suppression factor

For a fixed overall suppression factor 10For a fixed overall suppression factor 1033 of the full path of the full path

Calo rejection ~3, pixel rejection ~330, time ~175ms at high Calo rejection ~3, pixel rejection ~330, time ~175ms at high luminosityluminosity

Pile up tracks in isolation cone lead to some loss of signal efficiency at high luminosity for Calo-PXLPile up tracks in isolation cone lead to some loss of signal efficiency at high luminosity for Calo-PXL

L=2x10L=2x103333cmcm-2-2ss-1-1

L=1x10L=1x103434cmcm-2-2ss-1-1

0.410.41

0.330.33


By adding a few Tracker hits, can measure track momentum: By adding a few Tracker hits, can measure track momentum:

Cut on leading track Pt (>6,7 GeV) allows to reduce isolation Cut on leading track Pt (>6,7 GeV) allows to reduce isolation cone size => higher signal efficiency and less sensitivity to cone size => higher signal efficiency and less sensitivity to

pile-uppile-up

Calo-Trk ACalo-Trk A00/H/H00->2->2->2->2-jet-jet

Trk tau fast enough at low luminosity for full L1 rateTrk tau fast enough at low luminosity for full L1 rateAt high luminosity currently need a moderate Calo pre-selection factor to reduce time At high luminosity currently need a moderate Calo pre-selection factor to reduce time

Trk tau timing @ low lumi: QCD eventsTrk tau timing @ low lumi: QCD events Trk tau timing @ low lumi: signal eventsTrk tau timing @ low lumi: signal events

0.440.44

0.430.43

Low lumiLow lumi

High lumiHigh lumi


Inclusive b tagging at HLTInclusive b tagging at HLT(exclusive B’s see V.Ciulli’s talk)(exclusive B’s see V.Ciulli’s talk)

Inclusive b tag at HLT possible (provided alignment under control…)Inclusive b tag at HLT possible (provided alignment under control…)Now considering how to extend CMS (SUSY) physics reach using thisNow considering how to extend CMS (SUSY) physics reach using this

Use tracks to define Jet axisUse tracks to define Jet axis(if rely on L1 Calo Jet ~ randomize signed IP)(if rely on L1 Calo Jet ~ randomize signed IP)

Performance of simple signed IP “track counting” tagsPerformance of simple signed IP “track counting” tags~ same as after full track reconstruction~ same as after full track reconstruction

Regional Tracking: Look only inRegional Tracking: Look only inJet-track matching coneJet-track matching cone


Conditional Tracking: Stop track as soon asConditional Tracking: Stop track as soon asPixel seed found (PXL)Pixel seed found (PXL) / / 6 hits found (Trk)6 hits found (Trk)


~300ms low lumi~300ms low lumi~1s high lumi~1s high lumi


Radiation Length in the TrackerRadiation Length in the Tracker

As a result of the attention paid to controlling the material budgetAs a result of the attention paid to controlling the material budget

in the design of the CMS Tracker, nothing sticks out particularly.in the design of the CMS Tracker, nothing sticks out particularly.

It does, however, add up…It does, however, add up…


Electron reconstructionElectron reconstructionwith the CMS Trackerwith the CMS Tracker

For electrons, using Bethe and Heitler formula for energy loss (Yellow distribution)For electrons, using Bethe and Heitler formula for energy loss (Yellow distribution)works better than treating them as muons… (White distribution)works better than treating them as muons… (White distribution)

Can one do better?Can one do better?

The design is frozen (the Tracker is under construction!) and its “heavy”:The design is frozen (the Tracker is under construction!) and its “heavy”:How to make the best of it, also for electrons?How to make the best of it, also for electrons?



In the standard treatment, a single Gaussian is used to approximateIn the standard treatment, a single Gaussian is used to approximatethe underlying probability distributionthe underlying probability distribution

The energy loss of electrons in material is manifestly not well described by thisThe energy loss of electrons in material is manifestly not well described by this



Residual and probability distributions for a sample of 10 GeV electrons in the barrelResidual and probability distributions for a sample of 10 GeV electrons in the barrel

GSF significantly improves the resolution: FWHM is reduced by ~ factor of 2GSF significantly improves the resolution: FWHM is reduced by ~ factor of 2And provides a better estimate of the errorsAnd provides a better estimate of the errors

Gaussian Sum Filter (GSF)Gaussian Sum Filter (GSF)Approximate Bethe & Heitler with multiple GaussiansApproximate Bethe & Heitler with multiple Gaussians

At each material layer create and test new track hypotheses At each material layer create and test new track hypotheses corresponding to each of these Gaussianscorresponding to each of these Gaussians

Retain only “the best ones” (combinatorial reduction) and continueRetain only “the best ones” (combinatorial reduction) and continue


CMS Inner Tracking:CMS Inner Tracking:Summary and ConclusionsSummary and Conclusions

The CMS Silicon Tracker has robust performance in a difficult environmentThe CMS Silicon Tracker has robust performance in a difficult environment

The pixel vertex detector allows fast & efficient track seed generation,The pixel vertex detector allows fast & efficient track seed generation,

As well as excellent 3-D secondary vertex identificationAs well as excellent 3-D secondary vertex identification

The fine granularity of the pixel and strip sensors, together with the The fine granularity of the pixel and strip sensors, together with the analyzing power of the CMS 4T magnet allow for a ~ 2% or better Pt analyzing power of the CMS 4T magnet allow for a ~ 2% or better Pt

resolution for 100GeV muons over about 1.7 units of rapidityresolution for 100GeV muons over about 1.7 units of rapidity

A good determination of track parameters with only a few hits (4~6) allows A good determination of track parameters with only a few hits (4~6) allows fast & clean pattern recognitionfast & clean pattern recognition

This makes possible the extensive use of track information at HLT level for This makes possible the extensive use of track information at HLT level for essentially the full L1 output stream at both high and low luminosityessentially the full L1 output stream at both high and low luminosity

We are now studying how this may be used to improve and extend the We are now studying how this may be used to improve and extend the physics reach of the CMS experiment, in particular with jet flavor taggingphysics reach of the CMS experiment, in particular with jet flavor tagging

Documents

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 CMS Inner Tracking