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

High Luminosity Physics at the LHC “Golden Channel” pp & High luminosity => “mess” High Luminosity Physics at the LHC “Golden Channel” pp & High luminosity => “mess” Tracker Requirements: Efficient & robust Pattern Recognition algorithm ÞFine granularity to resolve nearby tracks ÞFast response time to resolve bunch crossings Ability to reconstruct narrow heavy object Þ 1~2% Pt resolution at ~ 100 Ge. V Ability to tag b/t through secondary vertex ÞGood impact parameter resolution This Review: HLT, including b & t jet tags Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

The CMS Pixel Vertex detector: Silicon strips have become pixels The region below 20 The CMS Pixel Vertex detector: Silicon strips have become pixels The region below 20 cm is instrumented with Silicon Pixel Vertex systems The Pixel area is driven by FE chip The shape is optimized for resolution 4 107 pixels CMS pixel ~ 150 * 150 mm 2 Shaping time ~ 25 ns With this cell size, and exploiting the large Lorentz angle We obtain IPtrans. resolution ~ 20 mm for tracks with Pt ~ 10 Ge. V m cm 30 c 30 With this cell size occupancy is ~ 10 -4 m 93 c Marcello Mannelli This makes Pixel seeding the fastest Starting point for track reconstruction Despite the extremely high track density CMS Inner Tracking LHC Symposium May 2003

From strip Vertex to strip Tracking Single-sided, AC coupled, polysilicon biased sensors have become From strip Vertex to strip Tracking Single-sided, AC coupled, polysilicon biased sensors have become a mature technology Costs have decreased, and large scale production is now possible High level of expertise for FE IC design and system aspects of O(10 5) channels Move to detectors with a high level of independent tracking capability 1. A few m 2 : 2. Several * 101 m 2 : 3. A couple * 102 m 2 : Marcello Mannelli CDF – D 0 CMS Inner Tracking ATLAS CMS LHC Symposium May 2003

The CMS Tracker: 220 m 2 of silicon strip sensors Outer Barrel –TOB- Pixel The CMS Tracker: 220 m 2 of silicon strip sensors Outer Barrel –TOB- Pixel End cap –TEC- Inner Barrel –TIB- 2, 4 m Inner Disks –TID- . 4 m 5 volume 24. 4 m 3 running temperature – 10 0 C dry atmosphere for YEARS! Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

SST Module level Components Silicon sensors 9’ 648’ 128 strips channels 75’ 376 APV SST Module level Components Silicon sensors 9’ 648’ 128 strips channels 75’ 376 APV chips Reliable, High Yield Industrial IC process 6’ 136 Thin sensors 18’ 192 Thick sensors CF frame 440 m 2 of silicon wafers 210 m 2 of silicon sensors Large scale 6” industrial sensor production 3’ 112 + 2*1’ 512 Thin modules 5’ 496 + 2*1’ 800 Thick modules ss ds=b-to-b FE hybrid with FE ASICS Pitch adapter Marcello Mannelli ~17’ 000 modules Automated module assembly ~25’ 000 Bonds State of the art Bonding machines CMS Inner Tracking LHC Symposium May 2003

The radiation hard P-on-N strip detector Single-Sided Lithographic Processing ( AC, Poly-Si biasing ) The radiation hard P-on-N strip detector Single-Sided Lithographic Processing ( AC, Poly-Si biasing ) Radiation hardness “recipe” Al Strips P-on-N sensors work after bulk type inversion, Provided they are biased well above depletion P+ implants Match sensor resistivity & thickness to fluence To optimize S/N over the full life-time Follow simple design rules for guard & strip geometry N Bulk Use Al layer as field plate to remove high field @edges from Si bulk to Oxide (much higher Vbreak) N+ Implants Surface damage P+ implants “P” Bulk +++ ----++ Strip width/pitch ~ 0. 25: reduce Ctot maintain Stable high bias voltage operation Take care with process: especially implants… +++++ ----- Use <100> crystal instead of <111> N+ Implants Marcello Mannelli Surface radiation damage can increase strip capacitance & noise CMS Inner Tracking LHC Symposium May 2003

Silicon Strip Sensor Properties Strip capacitance ~ 1. 2 p. F/cm for w/p = Silicon Strip Sensor Properties Strip capacitance ~ 1. 2 p. F/cm for w/p = 0. 25 Independent of pitch and thickness Use 320 mm thick Si for R < 60 cm, Strip ~ 10 cm Use 500 mm thick Si for R > 60 cm, Strip ~ 20 cm Marcello Mannelli CMS Inner Tracking Insensitive to irradiation for <100> crystal lattice Expected S/N after irradiation S/N ~ 13 for thin sensors, short strips S/N ~ 15 for thick sensors, long strips LHC Symposium May 2003

The CMS Silicon Strip Tracker: from 4” to 6” The CMS SST exploits 6” The CMS Silicon Strip Tracker: from 4” to 6” The CMS SST exploits 6” technology: Useful surface/wafer ~ 2. 5 * that of 4” wafers Large scale high quality sensor production in modern Industrial lines available from more than one vendor: Hamamatsu produces the “thin” 320 m sensors; ST-Microelectronics the “thick” 500 m sensors Production is well underway: Hamamatsu: excellent quality, some concerns regarding Selection of sufficiently low resistivity raw material ST: production quality also good, problems due To inappropriate manipulation of sensors during Testing are being addressed Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

Front-End Hybrids This has proven to be a major challenge, and has defined the Front-End Hybrids This has proven to be a major challenge, and has defined the Critical path for module assembly. We have finally converged on: • 4 layer Kapton flex circuit: • high resolution multi-layer Kapton circuits now available industrially in large volumes • “seamless” integration of flexible pig-tail • Laminated onto a ceramic substrate • need rigidity for bonding chips to hybrid • ceramic chosen since adequate thermally and mechanically (flatness!) and cheap • provides support for pitch adapter • can fully bond the hybrid to pitch-adapter assembly before gluing on module frame Pre-series production end of 2002 => Design fine-tuned for efficient lamination and component assembly and wire-bonding. Hybrid production now ramping up, module assembly following Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

The Gantry in action Assembly of 3 TOB Modules Glue dispensing syringes Sensor pick The Gantry in action Assembly of 3 TOB Modules Glue dispensing syringes Sensor pick up tool Tool rack Silicon sensors Hybrid pick up tool Assembly platform Carbon fiber frames Vacuum system Marcello Mannelli Hybrids CMS Inner Tracking LHC Symposium May 2003

Placement accuracy and reproducibility with automatic pattern recognition “Gantry see, Gantry do” The gantry Placement accuracy and reproducibility with automatic pattern recognition “Gantry see, Gantry do” The gantry system localizes automatically the components to be assembled by searching for a Marker with a camera Image found: place Sensor pair precisely Sensors within a module are placed to better than 5 m and 2 mr Relative to each other Miss-placements of up to 10 m do not significantly degrade the Ultimate muon Pt resolution even if not corrected for in track reconstruction s. DX 3 mm Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

S/N performance in System Tests S/N ~ 25 (20% higher than b rays) If S/N performance in System Tests S/N ~ 25 (20% higher than b rays) If muons (@ 500 mm) = 40000 electrons noise (@ deco) = 1600 electrons identical to predictions. Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

Basic design and performance considerations for the CMS Tracker To set the scale for Basic design and performance considerations for the CMS Tracker To set the scale for the momentum measurement, recall that: The CMS B Field = 4 T and the TK Radius ~ 110 cm result in: 1. 9 mm sagitta for 100 Ge. V Pt tracks (190 m sagitta for 1 Te. V Pt tracks) To set the scale for speed and granularity, recall that: At high luminosity expect ~ 20 min. bias events every 25 ns => a very high charged particle flux (modified the B field) R = 10 cm Nch/(cm 2*25 ns) = 1. 0 Marcello Mannelli CMS Inner Tracking 25 cm 0. 10 60 cm 0. 01 LHC Symposium May 2003

The CMS Tracking Strategy Rely on “few” measurement layers, each able to provide robust The CMS Tracking Strategy Rely on “few” measurement layers, each able to provide robust (clean) and precise coordinate determination 2 to 3 Silicon Pixel, and 10 to 14 Silicon Strip Measurement Layers Radius ~ 110 cm, Length ~ 270 cm R-phi (Z-phi) only measurement layers 6 layers TOB R-phi (Z-phi) & Stereo measurement layers h~2. 4 4 layers TIB 3 disks TID Marcello Mannelli h~1. 7 9 disks TEC CMS Inner Tracking LHC Symposium May 2003

Design considerations for CMS SST: Cell size & strip pitch Efficient & clean track Design considerations for CMS SST: Cell size & strip pitch Efficient & clean track reconstruction is ensured provided occupancy below few % DPt/ Pt ~ 0. 1*Pt (Pt in Te. V) allows to reconstruct Z to m+m- with Dm. Z < 2 Ge. V up to Pt ~ 500 Ge. V Twelve layers with (pitch/ 12) spatial resolution and 110 cm radius give a momentum resolution of At small radii need cell size < 1 cm 2 and fast (~25 ns) shaping time This condition is relaxed at large radii A typical pitch of order 100 mm is required in the phi coordinate To achieve the required resolution Strip length ranges from 10 cm in the inner layers to 20 cm in the outer layers. Pitch ranges from 80 mm in the inner layers to near 200 mm in the outer layers Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

Robust and clean hits Hit contamination is ~ 4% in the first Silicon Strip Robust and clean hits Hit contamination is ~ 4% in the first Silicon Strip layer Less than ~ 2% elsewhere 4% 2% Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

Partial Track reconstruction Good track parameter resolution already with 4 or more hits Marcello Partial Track reconstruction Good track parameter resolution already with 4 or more hits Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

Robust Pattern Recognition Well defined track parameters with 4 or more hits => Small Robust Pattern Recognition Well defined track parameters with 4 or more hits => Small uncertainties on the predicted track state 1 mm 400 m 200 m Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

Robust Pattern Recognition ~ 15 -20% of track candidates Are matched to a spurious Robust Pattern Recognition ~ 15 -20% of track candidates Are matched to a spurious hit Marcello Mannelli CMS Inner Tracking ~ 1% of track candidates Are matched to a spurious hit LHC Symposium May 2003

Robust Pattern Recognition Even in the most crowded situations, <10% of track candidates extrapolated Robust Pattern Recognition Even in the most crowded situations, <10% of track candidates extrapolated from Barrel Si Strip layer 1 are matched to a spurious hit Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

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

Track reconstruction efficiency in jets 95% Efficiency for particles in a 0. 4 cone Track reconstruction efficiency in jets 95% Efficiency for particles in a 0. 4 cone around jet axis No significant degradation compared to single pions Loss of efficiency is dominated by hadronic interactions in Tracker material Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

Impact Parameter resolution For 10 Ge. V Pt tracks, s(d 0) <30 m for Impact Parameter resolution For 10 Ge. V Pt tracks, s(d 0) <30 m for h<1. 5; degrading to ~ 40 m for h=2. 4 For 10 Ge. V Pt tracks, s(Z 0) <50 m for h<1. 5; degrading to ~150 m for h=2. 4 Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

Pt Resolution For High Momentum Muons The CMS Tracker provides ~ 1% Pt resolution Pt Resolution For High Momentum Muons The CMS Tracker provides ~ 1% Pt resolution over ~ 0. 9 units of h, and 2% Pt resolution up to h ~ 1. 75, beyond which the lever arm is reduced Even at 100 Ge. V muons are significantly affected by multiple scattering: a finer pitch, and higher channel count Would therefore yield only diminishing returns in improving the Pt resolution Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

Alignment tools and strategy Tools implemented to introduce, And account for, misalignments Following the Alignment tools and strategy Tools implemented to introduce, And account for, misalignments Following the hierarchical organization Of the mechanical degrees of freedom Inherent in the support structures Pattern recognition works efficiently and cleanly with misalignments of up to 1 mm, for W->mn events at 2*1033 This is the essential starting Point for alignment with tracks Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

High quality track reconstruction code Fully functional code released ~ January 2001 Good efficiency High quality track reconstruction code Fully functional code released ~ January 2001 Good efficiency and track quality Well designed modular architecture Excellent framework for systematic optimization Timing analysis: 85% in Trajectory building Dominated by search for compatible layers 5 times faster layer search => Overall 3 times faster reconstruction (at least in the barrel) <5% <10% >80% Example of technical improvements: Previous track propagator was “good enough for government work” New track propagator ~ perfect Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

The CMS Trigger and DAQ architecture Two level data reduction: Lvl-1 trigger & HLT The CMS Trigger and DAQ architecture Two level data reduction: Lvl-1 trigger & HLT filter Lvl-1 = “crude” granularity and Pt resolution: Rate dominated by miss-measured jets & leptons HLT task: reduce rate by ~ 1000 Exploit much better Granularity and Pt resolution to correctly tag and retain only interesting physics events 40 MHZ 50 KHz 100 Hz On average ~300 ms available for HLT Decision on any given event (Normalized to a 1 GHz Pentium) Marcello Mannelli CMS Inner Tracking 4 DAQ slices in 2007 => 50 KHZ into HLT, 100 Hz out LHC Symposium May 2003

Examples of Tracker @ HLT: tau tagging Regional Tracking: Look only in Jet-track matching Examples of Tracker @ HLT: tau tagging Regional Tracking: Look only in Jet-track matching cone Loose Primary Vertex association Conditional Tracking: Stop track as soon as Pixel seed found (PXL) / 6 hits found (Trk) If Pt<1 Ge. V with high C. L. Reject event if no “leading track” found Regional Tracking: Look only inside Isolation cone Loose Primary Vertex association Conditional Tracking: Stop track as soon as Pixel seed found (PXL) / 6 hits found (Trk) If Pt<1 Ge. V with high C. L. Reject event as soon as additional track found Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

Calo-PXL A 0/H 0 ->2 t jets Optimization of the Calo-PXL signal efficiency as Calo-PXL A 0/H 0 ->2 t jets Optimization of the Calo-PXL signal efficiency as a function of the Calo Tau Trigger suppression factor For a fixed overall suppression factor 103 of the full path Calo rejection ~3, pixel rejection ~330, time ~175 ms at high luminosity L=2 x 1033 cm-2 s-1 0. 41 L=1 x 1034 cm-2 s-1 0. 33 Pile up tracks in isolation cone lead to some loss of signal efficiency at high luminosity for Calo-PXL Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

Calo-Trk A 0/H 0 ->2 t-jet By adding a few Tracker hits, can measure Calo-Trk A 0/H 0 ->2 t-jet By adding a few Tracker hits, can measure track momentum: Cut on leading track Pt (>6, 7 Ge. V) allows to reduce isolation cone size => higher signal efficiency and less sensitivity to pile-up Low lumi 0. 44 High lumi 0. 43 Trk tau fast enough at low luminosity for full L 1 rate At high luminosity currently need a moderate Calo pre-selection factor to reduce time Trk tau timing @ low lumi: QCD events Marcello Mannelli CMS Inner Tracking Trk tau timing @ low lumi: signal events LHC Symposium May 2003

Inclusive b tagging at HLT (exclusive B’s see V. Ciulli’s talk) Regional Tracking: Look Inclusive b tagging at HLT (exclusive B’s see V. Ciulli’s talk) Regional Tracking: Look only in Jet-track matching cone Loose Primary Vertex association Conditional Tracking: Stop track as soon as Pixel seed found (PXL) / 6 hits found (Trk) If Pt<1 Ge. V with high C. L. ~300 ms low lumi ~1 s high lumi Performance of simple signed IP “track counting” tags ~ same as after full track reconstruction Use tracks to define Jet axis (if rely on L 1 Calo Jet ~ randomize signed IP) Inclusive b tag at HLT possible (provided alignment under control…) Now considering how to extend CMS (SUSY) physics reach using this Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

Radiation Length in the Tracker As a result of the attention paid to controlling Radiation Length in the Tracker As a result of the attention paid to controlling the material budget in the design of the CMS Tracker, nothing sticks out particularly. It does, however, add up… Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

Electron reconstruction with the CMS Tracker The design is frozen (the Tracker is under Electron reconstruction with the CMS Tracker The design is frozen (the Tracker is under construction!) and its “heavy”: How to make the best of it, also for electrons? For electrons, using Bethe and Heitler formula for energy loss (Yellow distribution) works better than treating them as muons… (White distribution) Can one do better? Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

Electron reconstruction with the CMS Tracker In the standard treatment, a single Gaussian is Electron reconstruction with the CMS Tracker In the standard treatment, a single Gaussian is used to approximate the underlying probability distribution The energy loss of electrons in material is manifestly not well described by this Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

Electron reconstruction with the CMS Tracker Gaussian Sum Filter (GSF) Approximate Bethe & Heitler Electron reconstruction with the CMS Tracker Gaussian Sum Filter (GSF) Approximate Bethe & Heitler with multiple Gaussians At each material layer create and test new track hypotheses corresponding to each of these Gaussians Retain only “the best ones” (combinatorial reduction) and continue Residual and probability distributions for a sample of 10 Ge. V electrons in the barrel GSF significantly improves the resolution: FWHM is reduced by ~ factor of 2 And provides a better estimate of the errors Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003

CMS Inner Tracking: Summary and Conclusions The CMS Silicon Tracker has robust performance in CMS Inner Tracking: Summary and Conclusions The CMS Silicon Tracker has robust performance in a difficult environment The pixel vertex detector allows fast & efficient track seed generation, As well as excellent 3 -D secondary vertex identification The fine granularity of the pixel and strip sensors, together with the analyzing power of the CMS 4 T magnet allow for a ~ 2% or better Pt resolution for 100 Ge. V muons over about 1. 7 units of rapidity A good determination of track parameters with only a few hits (4~6) allows fast & clean pattern recognition This makes possible the extensive use of track information at HLT level for essentially the full L 1 output stream at both high and low luminosity 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 tagging Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003