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Introduction to FTK: Enhancing Particle Detection at LHC - M. Shochet

Explore the key aspects of the Fast TracKer (FTK) system, its role in improving particle detection efficiency at LHC, challenges in handling 3rd generation particles, and the innovative pattern recognition and track fitting techniques used within FTK. Learn about the unique features, benefits, and implementation of FTK in the ATLAS framework.

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Introduction to FTK: Enhancing Particle Detection at LHC - M. Shochet

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  1. Introduction to FTK More technical description: http://www.pi.infn.it/~orso/ftk/ Introduction to FTK - M. Shochet

  2. What is the problem? • In hadron colliders, the “easy” triggers are e, , , & generic jets. • Is that good enough at the LHC? • Opening a new energy frontier. • SM  new physics, but what it is we don’t know •  don’t ignore 3rd generation partons (b, ) • ex: EWK symmetry breaking couples  mass  3rd generation important • ex: Introduction to FTK - M. Shochet

  3. Why is it hard to trigger on the 3rd generation? • b : jet Generic jets have production cross •  : narrow jet sections orders of magnitude larger. • To identify b-jets and -jets, need tracks. • b-jet: secondary vertex • -jet: ≤ 3 tracks in narrow cone; no tracks around it • 40 MHz interaction rate & 1 KHz level-2 accept rate  selection of b-jets and -jets must be done quickly! deadtime = L1 rate  L2 reject time As high as possible to lower PT threshold.  make as short as possible Introduction to FTK - M. Shochet

  4. Existing ATLAS (& CMS) Trigger • Track pattern recognition & fitting done in Intel PC’s. • 20-50 msec because of overhead of getting all of the raw silicon hits into the processor and sorted for track finding. TOO LONG! Introduction to FTK - M. Shochet

  5. FTK (Fast TracKer) • Based on the CDF SVT • Finds and reconstructs with near offline d0 precision all tracks of PT > 1.5 GeV/c in ~20 sec. sample for Bs mixing Z → bb Introduction to FTK - M. Shochet

  6. The Pattern Bank How does it work? • Complete pattern recognition on the fly as the silicon data passes by using pre-stored bank of possible hit patterns. • CDF: 32K patterns/phi sector → 15M in ATLAS made possible by advances in -electronics in past decade (prototype: SVT upgrade) Introduction to FTK - M. Shochet

  7. Pattern recognition in action Introduction to FTK - M. Shochet

  8. Track Fitting • Very fast: In CDF, 200 nsec/track using FPGA. • Narrow roads  linearized fit works well • Linear equations (a few hardware adds and multiplies) with pre-stored coefficients: curvature, d0, , 2. Track impact parameter  = 48m Introduction to FTK - M. Shochet

  9. Where does it fit in ATLAS? on L1 accept RODs SCT  Pixels  FTK “Level 1.5” ROBs ROBs silicon hits silicon tracks ask for ROI’s Level 2 Introduction to FTK - M. Shochet

  10. First Step: Making the Physics Case • ATLAS wants a few specific channels studied so the physics reach with and without FTK can be compared. • In discussion with the ATLAS Physics Coordinators and others, we came up with a “short list”. Introduction to FTK - M. Shochet

  11. for measuring the b-jet response and resolution (-jet & Z-jet balance have theory/exp problems) for Mtop , MHiggs , … Problem: L1 trigger rate  higher jet ET threshold high threshold  high MJJ turn-on Solution: high PT Z’s • 3-jet trigger • highest ET jet is not tagged • bb opening angle not fixed near 1800  lower MJJ threshold Introduction to FTK - M. Shochet

  12. Higgs Physics How much lower in tan can be reached? These jet PT’s are too low for existing triggers. How much does FTK help? Introduction to FTK - M. Shochet

  13.  leptons • Need lower threshold for all  triggers. How low can the threshold be? • (Fabiola) • for the high PT response of TileCal across the detector • Existing thresholds (35/45 GeV) too high for W’s • (More general: isolated track triggers for calorimeter calibration – rapid level-2 rejection  higher level-1 rate) • (Ian) Existing  trigger is for 1-prong only. Polarization information requires seeing other  decay modes. Introduction to FTK - M. Shochet

  14. More • (Michelangelo) B physics(if initial  is very low) ex, Introduction to FTK - M. Shochet

  15. What has to be done? What drives trigger decisions is background rejection, not signal efficiency. For signal, a few thousand events probably are enough. But background studies require LOTS of events. At 10 minutes/simulated event, … • Use fully simulated events to parameterize • jet response (with fluctuations) • jet trigger efficiency vs ET( especially at level 1) • Erik Brubaker is working on this. Use full simulation to parameterize FTK tracking: • Pisa will get the FTKsim tools working with current ATLAS software • then: tracking efficiency in jets, fake rate Then can do convincing physics studies with fast simulation. HOW?? (Iacopo) Introduction to FTK - M. Shochet

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