1. Tracker in the Trigger: from CDF experience to S-CMS Fabrizio Palla INFN – Pisa Vertex 2007 Lake Placid, NY, USA

2. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS The Tracker and the Trigger n Trigger rates control is extremely challenging in high luminosity hadron collider experiments u As the luminosity increases, physics goals change in response to new discoveries and the detector ages. n It is thus essential that the trigger system be flexible and robust, and have redundancy and significant operating margin u Providing high quality track reconstruction over the full detector can be an important element in achieving these goals. n This has certainly been the case in the CDF experiment where the Silicon Vertex Trigger (SVT) has significantly extended the experiment’s physics capability u B-physics and B s oscillations u Search for the Higgs boson n Even more challenging will be the trigger for the foreseen upgrade of LHC, the so-called SuperLHC (SLHC) u Luminosity increase of a factor 10 wrt “standard” LHC

3. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS 3cm 15cm 150cm Outer drift chamber Silicon  strip detector Silicon close-up Impact parameter Beam spot 1mm Zoom-in Input (every Level 1 accept):  XFT trajectories  silicon pulse height for each channel Output (about 20  s later):  trajectories that use silicon points  r-  tracks  impact parameter:  (d)=35  m AM algo SVT at CDF Level-2 Trigger

4. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS The Event... The Pattern Bank The pattern bank is flexible set of pre-calculated patterns:  can account for misalignment  changing detector conditions  beam movement  … Pattern matching in CDF (M. Dell’Orso, L. Ristori – 1985)

5. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS The Displaced Track Trigger @ CDF n Striking difference wrt D0 thanks to SVT n But also vs CDF:  Run II ~2000 B s  D s  vs 1 in Run I u Compare with only 10 times increased integrated luminosity n The trigger had a big impact Online  mass Phys. Rev. Lett. 97, 242003 (2006).

6. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS On the opposite side: FPGA for the same AMchip P. Giannetti et al. “A Programmable Associative Memory for Track Finding”, Nucl. Intsr. and Meth., vol. A413/2-3, pp.367-373, (1998). AM chips from 1992 to 2005 (90’s) Full custom VLSI chip - 0.7  m (INFN-Pisa) 128 patterns, 6x12bit words each 32k roads / wedge F. Morsani et al., “The AMchip: a Full-custom MOS VLSI Associative memory for Pattern Recognition”, IEEE Trans. on Nucl. Sci., vol. 39, pp. 795-797, (1992). In the middle: Standard Cell 0.18  m (INFN-Pisa)  5000 pattern/chip AMchip L.Sartori, A. Annovi et al., “A VLSI Processor for Fast Track Finding Based on Content Addressable Memories”, IEEE Transactions on Nuclear Science, Volume 53, Issue 4, Part 2, Aug. 2006 Page(s):2428 - 2433 NEXT: NEW VERSION For both L1 & L2

7. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS SLHC Level-1 Trigger issues @ 10 35  ~400 Minimum Bias events/bx (50 ns) [16xLHC] n Occupancy u Degraded performance of algorithms l Electrons: reduced rejection at fixed efficiency from isolation l Muons: increased background rates from accidental coincidences u Larger event size to be read out l New Tracker: higher channel count & occupancy  large factor l Reduces the max level-1 rate for fixed bandwidth readout n Trigger Rates u Try to hold max L1 rate at 100 kHz by increasing readout bandwidth u Implies raising E T thresholds on electrons, photons, muons, jets and use of less inclusive triggers l Need to compensate for larger interaction rate & degradation in algorithm performance due to occupancy

8. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Needs for a Tracker Trigger at SLHC Note limited rejection power (slope) without tracker information n Tracker needs to be rebuild due to radiation aging n Move some HLT algorithms into Level-1 or design new algorithms reflecting tracking trigger capabilities u See previous talk by Marcin Konecki n Proposed boundary conditions u Rebuild L1 processors u Maintain 100kHz limit u Increase latency to 6.4µs l ECAL digital pipeline holds 256 samples @ 40MHz From CMS-DAQ TDR L =10 34 cm -2 s -1

9. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Main issues for Tracker Trigger n Data Rate in Tracker Volume at SLHC  About 12,000 tracks per bunch crossing (50 ns) in the Tracker volume |  |<2.5 and ~400 primary vertices/bx l Needs high granularity information n Innermost radii (~ 3x10 15 n eq cm -2 ) u At 10 cm radius the rate is ~10 8 cm -2 s -1 giving ~6000 links @ 2.5 Gbps link speed– simply impossible to cope with n Push towards larger radii u Benefits for momentum measurement based trigger u Ideal to match with muon and calorimeter triggers u ~1 mm pointing resolution for z- larger than average 2 pileup interactions (~0.4 mm)  Still fairly nice impact parameter resolution in transverse plane (~100  m for 10 GeV muons) to get rid of muons from  and  decays Without pixel With pixel  (z 0 ) Without pixel With pixel  (d 0 )

10. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Tracking Trigger driving ideas  Design considerations:  Main usage for p T reconstruction  Need low occupancy and large lever- arm, rather than brilliant space-point resolution  Need to decrease Tracker material budget by a sizeable amount  multiple scattering will drive the momentum resolution below ~10 GeV  Reduce to a minimum (possibly null) Tracker trigger-only layers  Impact on the Tracker design  Two possible approaches  Tracker primitives  Full readout for trigger  Limited information Detector level data reduction  Selective readout using Mu or Calo information  Like CDF XFT

11. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Tracker primitives from CDF SVX approach 1 AM for each enough-small  Patterns Hits: position+time stamp All patterns inside a single chip N chips for N overlapping events (identified by the time stamp) Event1 AMchip1 Event2 AMchip2 Event3 AMchip3 EventN AMchipN Main problem: input Bandwidth  divide the detector in thin  sectors. Each AM searches in a small  OFF DETECTOR Data links

12. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Full readout option  Exercise using CMS layout but modified strip pitch:  From 40 to 90 cm radius  Conservative approach  Barrel coverage up to |  |<1.5  R=40 and 50 cm macro-pixel like sensors of 0.2x5 mm 2 cell size  R>50 cm strip like sensors 50  m x 10 cm cell size  Subdivide the detector in many  sectors  Keep data volume limited in each sector  Combine information from at least 3 layers out of 4 in each sector  Momentum resolution of ~ few (<10)% at 10 GeV/c  Granularity driven by the minimum measurable p T for triggering purposes, without loosing efficiency  70  sectors at the innermost radius  Well covering the bending of a track of 10 GeV p T and above

13. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Sensors and signal routing hybrid 5 cm 6 cm 200x5000  m 2 Readout chips Fiber(s) Smaller radius sensors Larger radius sensors Fiber(s) 32 bits sufficient to locate hit position in the sector and bx time stamp hybrid 6 cm 10 cm 50  m x 10 cm Readout chips fibers

14. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Occupancy  GEANT4 simulation of tracking layers  Includes material budget and loopers Radius (cm)Hit/module/bx a Rate*/module (Gbps)Rate*/sector (Gbps)No. data links † /layer 4043.6281703200 5033.5211303100 6025.5161755300 7020.2131104600 8016.611805300 9013.99603900 ª average number on minimum bias events, 50 ns bx *32 bits/hit † for a data link speed of 5 Gbps  Pros: same fiber links for data and trigger  Simple and elegant  Cons : large number of links needed  Need >=5Gbps laser drivers: 90 nm technology required  Allow for fluctuations: increase by ~1.5 ?  Laser driver power: commercial range from 330mW/fiber (4Gbps) to 700 mW/fiber (10Gbps) Current links in CMS Silicon Strip: 1300 @ 60 cm and 2600 @34 cm

15. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Conceptual design AM EV0 AM EV1 AM EV50...... Layer 0: ~35 fibers bringing ~20 Hits/50 ns 1 Hit/5 ns From other layers From other layers From other layers Distribute hits into different sets of storage units depending on EVent # Parallel IN Serial OUT...... Parallel IN Serial OUT Parallel IN Serial OUT 1 FPGA From Detector

16. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Reducing the data rate n Keeping all information u Send only cluster position l Need simple ASIC on chip to perform clustering l Reduction of a factor ~2 u Reducing the number of bits per hit l Possible if time stamp not needed è Only strips detectors (larger radii) è Reduction of a factor ~1.8 è Needs fast readout electronics u Overall a factor ~3.5 reduction feasible l Current GBT chip (Marchioro group) 2.56 Gbps for data n Local data reduction for trigger purposes only n Coarser granularity joining readout channels for trigger purposes n Exploit high vs low p T tracks patterns

17. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Board dimensions n Current board dimensions  About 30,000 patterns per AM chip required  Needed ~ 80 boards with ~40 AM chips each  3200 AM chips  The current AM for CDF holds ~5000 patterns/6 planes in 0.18  m technology  If developed in the 90 nm technology one could accommodate ~4 times more patterns/AM chip hence 30,000 for 4 planes  In order to evaluate the board dimensions need to define the granularity and the lowest p T threshold  For instance, a 50  m pitch on 4 detector planes and a p T threshold of 10 GeV needs ~90,000 patterns (needs 3 AM chips)

18. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS MIP Cluster width discrimination 90 cm 70 cm 50 cm 30 cm Discrimination of low p T tracks made directly on the strip detector by choosing suitable pitch values in the usual range for strip sensors.

19. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Cluster width results n In this region, using 50µm pitch, about 5% of the total particles leave cluster sizes with ≤2 strips u Huge reduction in trigger links n Once reduced to ~100 KHz, it would only need few fast readout links to readout the entire Tracker R(cm)Pitch (  m) Z coverage (cm) Data Rate /Layer (Gbps) 40 170350 60 200160 7090200160 90 20095 No. of links (5Gbps) ~ 150 for whole tracker Data rate per layer could be reduced by more than 1 order of magnitude wrt full readout case

20. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Coarser granularity Calorimeters and muon system is  =0.087x0.087 u Compromise with momentum resolution Sufficient to use O(500  m) at innermost radius (R~50 cm) for a precision of ~15% at 10 GeV l OR-ed readout of 10 strips – simple logic è Reduction of a factor 10 But  p T /p T  p T  solve reducing promotion of low p T tracks and kill photons from  , but not brilliant momentum resolution u Loss in precision recovered by adding in AND a electron or a muon directly adding other information in the AM chip “layer” l Natural with AM chips Silicon sensor OR AM chip Muon p T, 

21. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS A first idea on selective readout n Provide a Muon Track fast Tag (MTT) to be associated with hits in outermost Tracker layers u Need a new detector for MTT yet to be defined (2 layers of RPC?) n Still very preliminary need more thoughts u Electrons and Jets?

22. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Stacked readout for Trigger n Angle  determines p T of track, assuming tracks coming from origin u Smaller a = greater pT n Pair of sensor planes at ~ mm distance for local p T estimate u Needs a correlator ASIC u Fast data links l If located at ~20 cm needs 3 Gbps n Stacks of 2 sensor planes at ~cm distance to be correlated (off detector) for p T measurement n Tight construction tolerances required for both sensors and their alignment u See M. Mannelli talk

23. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Conclusions n Tracker information helps reducing drastically the rate of uninteresting events u CDF SVT experience has become cornerstone for Tracker Trigger l B physics reach has been boosted after the usage of displaced vertex triggers and now Higgs search uses it n S-CMS will make use of tracking information at SLHC and has started to discuss several options u Triggering at SLHC is challenging due to fantastic data rate u Concentrate on momentum resolution, muon and electron matching u SVT approach seems feasible, especially if complemented by a data reduction at the module level u The trigger design and the detector layout are completely interleaved and are influencing each other u Next steps will involve simulating trigger with different layouts and are going to define which strategy will be used, stay tuned!

24. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS BACKUP

25. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS L at end of year time to halve error integrated L radiation damage limit ~700 fb-1 (1) LHC IR quads life expectancy estimated <10 years from radiation dose (2) the statistical error halving time will exceed 5 years by 2011-2012 (3) therefore, it is reasonable to plan a machine luminosity upgrade based on new low-  IR magnets by ~2016 design luminosity ultimate luminosity courtesy J. Strait Modified (start date) by F. Palla ultimate vs. design Time Scale of LHC Upgrade 2010 2012 2014 2016 2018 2020

26. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS switch board numbers All info here TBC with simulation and R&D! 80 switch boards 1 /  -sector 80 fibers / board assume 5Gbps each 40 AMchip / board now we can fit 32 AMchips in one 4 th of a 9U VME board 4 FPGA switches (1/layer) Each receiving ~20 fibers, i.e. ~100Gbps 40 outputs: one per Amchip Possible with today’s FPGAs 32 AMchips

27. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Dedicated device: maximum parallelism Each pattern with private comparator Track search during detector readout If you can read it out you can track it! AM: Associative Memory Bingo scorecard

28. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Associative Memory (AM) for pattern matching ~ Bingo game BINGO PLAYERS Dedicated device: Maximum parallelism ! Each pattern with private comparator Tracks found during detector readout ! M. Dell'Orso and L. Ristori, “VLSI structures for track finding”, Nucl. Instr. and Meth., vol. A278, pp. 436-440, (1989).

29. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Level 1 drift chamber trigger (XFT) 1 1.5 2 2.5 3 3.5 4 offline transverse momentum (GeV) XFT efficiency Finds p T >1.5 GeV tracks in 1.9  s For every bunch crossing (132 ns)!  (1/p T ) = 1.7%/GeV  (  0 ) = 5 mrad 96% efficiency

30. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS PD TIB TOB TOB TID TIB TEC PD 210m 2 micro-strip silicon detectors 15.232 modules 6136 320  m thick and 18.192 500  m thick sensors (all from 6” wafers). 7.136 APV chips 9.648.128 analog strip channels. About 25M wire bonding. The CMS Silicon Tracker at LHC 220 cm 270 cm

31. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS SLHC Trigger Requirements n High-p T discovery physics u Need high thresholds n Completion of LHC physics program u Example: precise measurements of Higgs sector u Require low thresholds on leptons/photons/jets l Use more exclusive triggers since final states will be known l Still an issue for L1 n Control & Calibration triggers u W, Z, Top events u Low threshold but prescaled

32. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Too large AM? 2 step approach 1.Find low resolution track candidates called “roads”. Solve most of the pattern recognition 2.Then fit tracks inside roads. Thanks to 1 st step it is much easier Super Bin (SB) OTHER functions are needed inside SVT: Hit Buffer + Track fitter + Hit Finder

33. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Latency  ~100 m fiber 300 ns [6 bx]  Switch + AM ~1  s [20 bx]  Sensor read-out latency budget should be less than ~20 bx  TOTAL ~ <50 bx [2.5  s]

34. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS

35. F. Palla INFN Pisa Vertex 2007, 23-28 September 2007 Tracker in the Trigger: from CDF to S-CMS Stacked trigger