1. More technical description: http://www.pi.infn.it/~orso/ftk/
Introduction to FTK
More technical description:
March 9, 2005
Introduction to FTK - M. Shochet

2. Introduction to FTK - M. Shochet
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:
March 9, 2005
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
March 9, 2005
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!
March 9, 2005
Introduction to FTK - M. Shochet

5. Introduction to FTK - M. Shochet
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
March 9, 2005
Introduction to FTK - M. Shochet

6. (prototype: SVT upgrade)
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)
The Pattern Bank
March 9, 2005
Introduction to FTK - M. Shochet

7. Pattern recognition in action
March 9, 2005
Introduction to FTK - M. Shochet

8. Introduction to FTK - M. Shochet
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
March 9, 2005
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
March 9, 2005
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”.
March 9, 2005
Introduction to FTK - M. Shochet

11. Introduction to FTK - M. Shochet
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
March 9, 2005
Introduction to FTK - M. Shochet

12. Introduction to FTK - M. Shochet
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?
March 9, 2005
Introduction to FTK - M. Shochet

13. Introduction to FTK - M. Shochet
 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.
March 9, 2005
Introduction to FTK - M. Shochet

14. Introduction to FTK - M. Shochet
More
(Michelangelo) B physics (if initial  is very low)
ex,
March 9, 2005
Introduction to FTK - M. Shochet

15. Introduction to FTK - M. Shochet
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)
March 9, 2005
Introduction to FTK - M. Shochet