# Presentation: 166853

## Fast on-line tracking in CDF

- Giovanni Punzi
- SNS and INFN - Pisa

- Giovanni Punzi - Pisa

- 27 Set. 2001

## Outline

- CDF and the Silicon Vertex Trigger (SVT)
- SVT is part of CDF Trigger for run II, begun this year
- Motivations for high-precision online tracking in CDF
- Design:
- Environmental constraints
- The solution: what is special about it
- Physics expectations
- Construction and Operation experience
- Performance
-  first results from real Tevatron data in 2000 and 2001
- Conclusions

- Giovanni Punzi - Pisa

- 27 Set. 2001

## Quadrant of CDF II Tracker

**-****COT: Drift chamber axial+stereo wires**
** ****-SVXII + ISL**
**	****6+3 Si microstrip**
**	****2-sides **
**	****	****90deg/stereo**
** ****-L00:**
**	****Innermost, 1-sided**** **

- Giovanni Punzi - Pisa

- 27 Set. 2001

## The Idea of SVT

**Goal: Extend CDF B-physics reach**
- B production at Tevatron large but:
-  QCD background is 1000x larger
-  trigger on (stiff/2) leptons  low efficiency
**Idea:** Trigger on _Impact Parameter_
- Build a fast device to do SVX tracking *online*
- Useful tool beyond i.p. (e.g. lepton confirmation)
- Need I.P. resolution ~offline
*** **all* parameters well measured

***B***

***B***

- Primary Vertex

- Secondary Vertex

**i.p. ********100********m**

- c450m

- Giovanni Punzi - Pisa

- 27 Set. 2001

## SVT Design Constraints

- Detector
- Raw Data

- Level 1
- pipeline:
- 42 clock
- cycles

- Level 1
- Trigger

- L1
- Accept

- Level 2
- Trigger

- Level 2 buffer: 4 events

- L2
- Accept

- DAQ buffers

- L3 Farm

- Level 1
- 7.6 MHz Synchromous Pipeline
- 5544 ns Latency
- 50 KHz accept rate

- Level 2
-  Asynchromous 2 Stage Pipeline
- 20 s Latency
- 300 Hz accept rate

- Mass Storage (50~100 Hz)

- 7.6 MHz Crossing  rate

- O(103) SVX strips/event
- Resolution offline
- 2-D low-res COT tracks
- 50 kHz input rate
- Latency 10 sec
- No Dead Time

- SVX read out after L1

- At L3 it is too late

- SVT here

- Giovanni Punzi - Pisa

- 27 Set. 2001

## SVT: Silicon Vertex Tracker(Chicago-Geneva-Pisa-Roma-Trieste)

- SVT: Silicon Vertex Tracker(Chicago-Geneva-Pisa-Roma-Trieste)

***SVX***

***SVX Hits***

**Roads**

***COT *****Tracks**

***ASSOCIATIVE***

***MEMORY***

**Tracks**

***HIT****** ***

***BUFFERS***

- TRACK

***FITTERS***

-  **Asynchronous data-driven pipeline**
-  Hit Finder: “on the fly” cluster finding
-  Associative Memory: real-time pattern
-   recognition at low resolution
-  Hit Buffer: associates hits to the roads
-    found by the Associative Memory.
-  Track Fitter: full-resolution fit

**Roads +hits**

***x 12 phi sectors***

- 1st:  find low-res tracks
- 2nd: fit for best resolution

**SVT**

*The SVT way*

**to L2**

- Giovanni Punzi - Pisa

- 27 Set. 2001

## The SVT Algorithm (Step I)Fast pattern Recognition

- Coarse resolution at this stage
- Hardware implementation via  totally parallel lookup table (Associative Memory)

- Limit to 2-D
- 6 layers:  5 SVX + 1 COT
- ~250 micron bins 	 32k roads / 300 slice
- >95% coverage for Pt>2GeV

- Giovanni Punzi - Pisa

- 27 Set. 2001

## Associative Memory internal structure

**Associative Memory internal structure**

**HIT COUNTER**

**AB<6:0>** **(OUTPUT MODE)**

**ADDRESS ENCODER**

**pattern 0**

**12 bits word**
**12 bits compar.**

**COUNT**

**SHIFT**

**pattern 1**

**pattern 127**

**HIT**
**BIT**

**DB<11:0>**

**DATA BUS MULTIPLEXER**

**ADDRESS DECODER**

**AB<6:0>** **( R/W MODE)**

**SELECT PLANE**
**DECODER**

**SELP<2:0>**

**MATCH BIT**

**layer0**

**layer1**

**layer3**

**layer2**

**layer4**

**layer5**

**HIT**
**BIT**

**HIT**
**BIT**

**12 bits word**
**12 bits compar.**

**12 bits word**
**12 bits compar.**

- Giovanni Punzi - Pisa

- 27 Set. 2001

## The SVT Algorithm (Step II)Track Fitting

- When the track is confined to a road, fitting becomes easy !
- Linear expansion in the hit positions xi:
- Chi2 = Sumk ( (cik xi)^2 ) => cut for final pattern recognition
- d = d0+ai xi ;  phi = phi0+ bi xi , Pt =.....
- Actually good over a wide range ( 30 degrees !)
- Fit reduces to a few scalar products-> fast evaluation
- (DSP, FPGA ...)
- Constants from detector geometry
- Calculate in advance
- Correction of mechanical alignments via linear algorithm
- fast and stable
- A tough problem made easy !

- Giovanni Punzi - Pisa

- 27 Set. 2001

## Impact parameter

- SVT was designed with B-physics in mind : focus on I.P.

_**SVT simulation on real data**_
_**Performance  =  offline !**_

-  ~ 45 m

- Giovanni Punzi - Pisa

- 27 Set. 2001

## Physics Prospects: All-Hadronic B decay Trigger

**Impact parameter from the SVT**

**Trigger on secondary vertices (B hadrons)**

**B**

**0**

****

**d**

**B**

**0**

**s**

**D  n******

**Level 1:****  2D COT tracks (XFT)**

** ****Two stiff tracks  (P****t**** > 2.0 GeV/c)**
** ****Remove back-to-back pairs ( ********< 135  )**
** ****Opposite charge**

**Level 2:****  SVT tracks**

** ****Two tracks with ****large impact parameter**
** ****Vertex tracks - require positive decay length**

**Trigger**** ****Strategy**

**o**

**s**

**( CP**** ****Violation)**

**Level 3: ****full event reconstruction**

**Z          bb**

**0**

**H          bb**

**(b-jet calibration **
**/ top mass)**

- Giovanni Punzi - Pisa

- 27 Set. 2001

_**The SVT advantage:**_
_**3 orders of magnitude**_

- Giovanni Punzi - Pisa

- 27 Set. 2001

## Expectations for runII

**- Level 1: 20 kHz  (bw  50 kHz)**
**- Level 2: 39 Hz    (bw  300 Hz)**
**- Level 3: negligible**
**Expected yields in run II (2 fb****-1****)**
**  **Mode**                     **Events
**  ****B****d**  ******************             15,200**
**  ****B****s  ** **D****s****  ********            10,600**
**  ****B****s**  **D****s  ********        12,800**
**  ****B****s  ** **D*********s****  ********            9,400**
**  ****D***** ********	****	****  300,000**
**  ****Z  **  b-bbar	    **32,000**

**Expectations for runII**

_**5**__****__** sensitivity up to **__***x***__***s***__** ~ 40**_

_**N.B. : yields without SVT **__****__** **__**O(1) event !**_

_**angle **__****__**  at few degrees level**_

****
****
****

- Giovanni Punzi - Pisa

- 27 Set. 2001

## SVT for Real

**>100 9Ux400mm Eurocard boards (8 kinds)**
**Data flow on dedicated point-to-point cable connections**
**VME used for download/control/diagnostics.**

- Giovanni Punzi - Pisa

- 27 Set. 2001

## CDF Trigger Room

- SVT

- Giovanni Punzi - Pisa

- 27 Set. 2001

## Commissioning

_**October 2000:**_ SVT completed. HW/data-flow test
- SVX “barrel 4”
- Only 2 phi slices, lower grade detectors
- No XFT tracks to SVT  Revert to SVX-only tracking !!
_**March 2001:**_**  ****Run II** starts (slowly)
- SVX coverage ~50%
- L2 decision not yet functional:
- Cannot correct for beam offset  make SVT do it
- Cannot cut on i.p./generate trigger  make SVT do it
- L3 farm cannot yet fit SVX tracks: too slow
- Use SVT tracks for L3 cuts, too

- Giovanni Punzi - Pisa

- 27 Set. 2001

## SVT Performance 2001 (II)Beam subtraction: d vs  SVX+XFT

- d= x0cos  + y0sin 
-  Beam position (x0, y0) computed in real time in crate CPU, subtracted by SVT
- Original plan was to do it in L2 processors

- COT HV
- problem

****

**d**

****

**d**

- Giovanni Punzi - Pisa

- 27 Set. 2001

## Start of RunII

**Start of RunII**

-  ~ 48 m

- Impact Parameter Distribution SVT data run 127844
- No alignment corrections

- What we promised.... From SVT TDR (’96) using offline silicon hits and offline CTC tracks

-  ~ 45 m

- Giovanni Punzi - Pisa

- 27 Set. 2001

**Notes:**
Metterci anche quella con SVX-only

## SVT Performance 2001 (I)Online Data: d vs  SVX Only

- Good tracks from just 4 closely spaced silicon layers
- I.p. as expected due to the lack of curvature information

- impact parameter distribution

-  ~ 87 m

- Giovanni Punzi - Pisa

- 27 Set. 2001

## SVT performanceNot just impact parameter

- :  SVT – COT

- Curvature: SVT - COT

- Loop on all SVT-COT track pairs and compare parameters

- Giovanni Punzi - Pisa

- 27 Set. 2001

## SVT vs offline

- Important test:
- Compare SVT impact parameter to offline SVX+COT
- Starting only in latest period:
- need to wait for offline tracking production
- Preliminary results :
- Loose cuts, corrections still missing
- Already obtain good match.
- Negligible tails.

- Giovanni Punzi - Pisa

- 27 Set. 2001

## SVT I.P. - Offline I.P.

-  ~ 22 m

- Giovanni Punzi - Pisa

- 27 Set. 2001

## SVT Performance On-line Impact Parameter Cut

**SVT Performance ****On-line Impact Parameter Cut**

-   Achieved by:
-  internal reprogram SVT
-  bypass L2 final logic
-  interface to L2 Trigger Supervisor
-  All on ~1 month timescale

- Trigger cuts ±50μm

- Giovanni Punzi - Pisa

- 27 Set. 2001

## Conclusion

- Online tracking with offline quality is a reality.
- We are very glad we built the SVT.

- Giovanni Punzi - Pisa

- 27 Set. 2001