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” Tracker Requirements: Efficient & robust Pattern Recognition algorithm  Fine granularity to resolve nearby tracks  Fast response time to resolve bunch crossings Ability to reconstruct narrow heavy object  1~2% Pt resolution at ~ 100GeV Ability to tag b/  through secondary vertex  Good impact parameter resolution This Review: HLT, including b &  jet tags pp & High luminosity => “mess”

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

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 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  A few m 2 :CDF – D0  Several * 10 1 m 2 :ATLAS  A couple * 10 2 m 2 :CMS

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 The CMS Tracker : 220m 2 of silicon strip sensors 5.4 m Outer Barrel –TOB- Inner Barrel –TIB- End cap –TEC- Pixel 2,4 m volume 24.4 m 3 running temperature – 10 0 C dry atmosphere for YEARS! Inner Disks –TID-

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

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 The radiation hard P-on-N strip detector Single-Sided Lithographic Processing ( AC, Poly-Si biasing ) N Bulk N+ Implants P+ implants Al Strips “P” Bulk N+ Implants P+ implants Surface damage Radiation hardness “recipe” P-on-N sensors work after bulk type inversion, Provided they are biased well above depletion Match sensor resistivity & thickness to fluence To optimize S/N over the full life-time Follow simple design rules for guard & strip geometry Use Al layer as field plate to remove high from Si bulk to Oxide (much higher V break ) Strip width/pitch ~ 0.25: reduce C tot maintain Stable high bias voltage operation Take care with process: especially implants… Surface radiation damage can increase strip capacitance & noise Use crystal instead of Use crystal instead of

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 Silicon Strip Sensor Properties Strip capacitance ~ 1.2pF/cm for w/p = 0.25 Independent of pitch and thickness Use  m thick Si for R < 60cm, Strip ~ 10cm Use  m thick Si for R > 60cm, Strip ~ 20cm Expected S/N after irradiation S/N ~ 13 for thin sensors, short strips S/N ~ 15 for thick sensors, long strips Insensitive to irradiation for crystal lattice

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 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  sensors; ST-Microelectronics the “thick” 500  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 Critical path for module assembly. We have finally converged on: 4 layer Kapton flex circuit: 4 layer Kapton flex circuit: high resolution multi-layer Kapton circuits now available industrially in large volumes high resolution multi-layer Kapton circuits now available industrially in large volumes “seamless” integration of flexible pig-tail“seamless” integration of flexible pig-tail Laminated onto a ceramic substrate Laminated onto a ceramic substrate need rigidity for bonding chips to hybrid need rigidity for bonding chips to hybrid ceramic chosen since adequate thermally and mechanically (flatness!) and cheapceramic chosen since adequate thermally and mechanically (flatness!) and cheap provides support for pitch adapter provides support for pitch adapter can fully bond the hybrid to pitch-adapter assembly before gluing on module frame 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 Assembly platform Carbon fiber frames Hybrids Silicon sensors Tool rack Glue dispensing syringes Sensor pick up tool Hybrid pick up tool Vacuum system

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

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 S/N performance in System Tests S/N ~ 25 (20% higher than  rays) If muons 500  m) = 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 the momentum measurement, recall that: The CMS B Field = 4T and the TK Radius ~ 110 cm result in: 1.9mm sagitta for 100 GeV P t tracks (190  sagitta for 1 TeV P t tracks) To set the scale for speed and granularity, recall that: At high luminosity expect ~ 20 min. bias events every 25ns => a very high charged particle flux (modified the B field) R = 10cm 25cm 60cm R = 10cm 25cm 60cm N ch /(cm 2 *25ns) = N ch /(cm 2 *25ns) =

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 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 6 layers TOB 4 layers TIB 3 disks TID 9 disks TEC R-phi (Z-phi) only measurement layers R-phi (Z-phi) & Stereo measurement layers Radius ~ 110cm, Length ~ 270cm  ~1.7  ~2.4

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 Design considerations for CMS SST: Cell size & strip pitch Efficient & clean track reconstruction is ensured provided occupancy below few % At small radii need cell size < 1cm 2 and fast (~25ns) shaping time This condition is relaxed at large radii  P t / P t ~ 0.1*P t (P t in TeV) allows to reconstruct Z to     with  m Z < 2GeV up to P t ~ 500GeV Twelve layers with (pitch/  12) spatial resolution and 110cm radius give a momentum resolution of A typical pitch of order  m 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  m in the inner layers to near 200  m 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 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 Mannelli CMS Inner Tracking LHC Symposium May 2003 Robust Pattern Recognition Well defined track parameters with 4 or more hits => Small uncertainties on the predicted track state 1mm 200  1mm 400 

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 Robust Pattern Recognition Includes “empty” hit Extrapolation to Pixel Layer 3 is matched to a spurious hit in less than 5% of the cases

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

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 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 efficiency in jets 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 95%95%

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 Impact Parameter resolution For 10 GeV Pt tracks,  (d 0 ) <30  for  <1.5; degrading to ~ 40  for  =2.4 For 10 GeV Pt tracks,  (Z 0 ) <50  for  <1.5; degrading to ~150  for  =2.4

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 Pt Resolution For High Momentum Muons The CMS Tracker provides ~ 1% Pt resolution over ~ 0.9 units of , and 2% Pt resolution up to  ~ 1.75, beyond which the lever arm is reduced Even at 100 GeV 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 Pattern recognition works efficiently and cleanly with misalignments of up to 1mm, for W->  events at 2*10 33 This is the essential starting Point for alignment with tracks Tools implemented to introduce, And account for, misalignments Following the hierarchical organization Of the mechanical degrees of freedom Inherent in the support structures

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 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 >80% <5% <10% 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) 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 MHZ 50 KHz 100 Hz 4 DAQ slices in 2007 => 50 KHZ into HLT, 100 Hz out The CMS Trigger and DAQ architecture Two level data reduction: Lvl-1 trigger & HLT filter On average ~300ms available for HLT Decision on any given event (Normalized to a 1GHz Pentium) 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

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 Examples of 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 GeV 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 GeV 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  ->2  jets Optimization of the Calo-PXL signal efficiency as a function of the Calo Tau Trigger suppression factor For a fixed overall suppression factor 10 3 of the full path Calo rejection ~3, pixel rejection ~330, time ~175ms at high luminosity Pile up tracks in isolation cone lead to some loss of signal efficiency at high luminosity for Calo-PXL L=2x10 33 cm -2 s -1 L=1x10 34 cm -2 s

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 By adding a few Tracker hits, can measure track momentum: Cut on leading track Pt (>6,7 GeV) allows to reduce isolation cone size => higher signal efficiency and less sensitivity to pile-up Calo-Trk A 0 /H 0 ->2  ->2  -jet Trk tau fast enough at low luminosity for full L1 rate At high luminosity currently need a moderate Calo pre-selection factor to reduce time Trk tau low lumi: QCD events Trk tau low lumi: signal events Low lumi High lumi

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 Inclusive b tagging at HLT (exclusive B’s see V.Ciulli’s talk) Inclusive b tag at HLT possible (provided alignment under control…) Now considering how to extend CMS (SUSY) physics reach using this Use tracks to define Jet axis (if rely on L1 Calo Jet ~ randomize signed IP) Performance of simple signed IP “track counting” tags ~ same as after full track reconstruction 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 GeV with high C.L. ~300ms low lumi ~1s high lumi

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 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 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? The design is frozen (the Tracker is under construction!) and its “heavy”: How to make the best of it, also for electrons?

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 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 Residual and probability distributions for a sample of 10 GeV electrons in the barrel GSF significantly improves the resolution: FWHM is reduced by ~ factor of 2 And provides a better estimate of the errors 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

Marcello Mannelli CMS Inner Tracking LHC Symposium May 2003 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 4T magnet allow for a ~ 2% or better Pt resolution for 100GeV 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 L1 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