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Introduction to FTK

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

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Introduction to FTK

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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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