L1 Trigger Strategy Ted Liu, Lawrence Berkeley Lab (for the trigger group) L1 Trigger Requirements and Trigger Lines L1 Trigger performance Background Study Improving Performance: near-term strategy Future Prospect: long-term strategy summary T. Liu, Oct. 99, L1 Strategy

L1 Performance Overview Still at 700 Hz after recent lumi&current increase: HER: 450 -> 600 mA LER: 800 -> 1000mA Pessimistic extrapolation to design current: HER +450*(750/600)2 700 LER +150*(2000/1000)2 600 Cosmics 150 Bhabha+Physics 250 TOTAL 1700 Hz We are in good shape, but can do better --> room for improvements Near-term concern T. Liu, Oct. 99, L1 Strategy Long-term concern

The Game is to Reduce rate as much as possible Bunch X: 238 MHz L1: < 2 KHz L3: < 100 Hz OPR: ~ 50 Hz? OFFLINE: ~ 2 Hz The Game is to Reduce rate as much as possible at each stage, and make life much easier downstream ! T. Liu, Oct. 99, L1 Strategy

Trigger Line Definition/Convention DCT Objects: B: short track reaching SL5, Pt ~120 MeV A: long track reaching SL10, Pt ~180 MeV A’: high Pt track reaching SL10, Pt > 800 MeV EMT Objects: M: minimal ionizing cluster, E >100 MeV G: intermediate energy cluster, E >300 MeV E: high energy cluster, E >700 MeV Y: backward barrel cluster, E >1 GeV IFT Objects: 1U: 1 high P muon in backward endcap o B*,M*...* means back-to-back objects(>120 ) D2 = 2B&1A, D2* = B*&1A D2*+ = B*&1A&1A’ , A+ = A&A’ T. Liu, Oct. 99, L1 Strategy

Trigger Lines for Hadronic Events run9304 Requirements: B Physics Pure DCT CP Channels: high eff. Non-CP channels: high + precise eff. DCT + EMT Continuum High & precise eff. for background sub. Pure EMT Strategy for eff. Measurements: orthogonal lines redundant lines record all trigger DAQ data prescaled lines T. Liu, Oct. 99, L1 Strategy

Use orthogonal DCT-EMT lines to study eff. From Su Dong Total eff for hadron skim: (EMT OR DCT) > 99.3% T. Liu, Oct. 99, L1 Strategy

Trigger Lines for non-physics Events run9304 Trigger Lines for non-physics Events Requirements: Luminosity, calibration: 2-prong ee, High + precise eff. Pure DCT Calibration, beam monitor: 1-prong ee, DCT + EMT  only Pure EMT Background monitoring Background&Trigger studies T. Liu, Oct. 99, L1 Strategy

Trigger Lines for  and 2 Events Requirements:  Physics Pure DCT Rare & Asy.: high eff. Branch Ratios: precise eff. DCT + EMT 2 Physics precise eff. Pure EMT Shortcomings: All unprescaled lines have high Pt cut (800MeV) and with back-to-back requirement. No unprescaled orthogonal lines. All high eff. Lines have to be prescaled. Expected @ high background rate, will try to improve… add 2BM+1AM, lower Pt cut? T. Liu, Oct. 99, L1 Strategy

Need good understanding of background --> next L1 Strategy to improve performance Better Combination of trigger lines: DCT+EMT phi matching Give up some orthogonal lines ... Improve trigger objects: Short-term: PTD ---> DOCAD Long-term: DOCAD --> DOCAZD? Need good understanding of background --> next T. Liu, Oct. 99, L1 Strategy

Single beam L1 pass thr. events Z distribution LER HER LER HER From S. Petrak T. Liu, Oct. 99, L1 Strategy

Many tracks from beampipe: off Z --> off IP in x-y LER HER LER HER Single beam L1 pass thr. events x-z view T. Liu, Oct. 99, L1 Strategy Many tracks from beampipe: off Z --> off IP in x-y

DCT Trigger Hardware GLT A’ PT Discriminator PTD (x8) DOCAD Drift Chamber DCT Trigger Hardware Binary Track Linker (BLT x1) Coarse data for all supercell hits Trigger data 24 Gbits/s A, B 16 GLT 16 A’ Fine position data for segments found for axial SLs PT Discriminator PTD (x8) New idea T. Liu, Oct. 99, L1 Strategy DOCAD Track Segment Finder (x24) (only firmware change)

Drift Chamber Trigger ( DCT ) The heart of DCT is the Track Segment Finder TSF continuously live image processor A novel method: using both occupancy and drift-time information, to find track segments continuously with: time resolution of ~ 100 ns, event-time jitter window ~ 100 ns spatial resolution ~ 1 mm used for track Pt Discrimination (1) send segment patterns downstream for L1 trigger decision making Upon a L1 accept: (2) send segment patterns to the DAQ system for use in Level 3 ... Track Segment Finder T. Liu, Oct. 99, L1 Strategy Use 24 TSF modules

T. Liu, Oct. 99, L1 Strategy

T. Liu, Oct. 99, L1 Strategy

(baseline design: simple algo.) Current PTD algorithm New DOCAD algorithm (baseline design: simple algo.) A10 seed x x 800MeV Pt threshold (800MeV) 850MeV SL7 900MeV SL7 1 GeV SL4 SL4 SL1 SL1 x x IP IP 4 hits on one track with ~1mm, should be able to tell whether the track is from IP Tracks (above threshold) coming from IP should leave all the hits in one of the slices Tracks not coming from IP will most likely leave hits in different slices T. Liu, Oct. 99, L1 Strategy

LER single beam run: background Apply DOCAD algorithm to TSF data Hadron skim: signal Effect on Signal: PTD on Use hadron skim (~10% bkg) ~ 4% loss at turn on DOCAD on Effect on Background: Use single beam run L1 pass thr events Max Pt in the event 40% rejection on A’ line with simple algorithm PTD on Background rejection: 40% The goal here is not to find the best algorithm possible, but one which is easy to be implemented and with good performance DOCAD on T. Liu, Oct. 99, L1 Strategy LER single beam run: background

4% rejected signal events are picked up by other lines Hadron skim Only one event out of 10**4 is lost T. Liu, Oct. 99, L1 Strategy New DOCAD algorithm is SAFE for signal events

Some rejected bkg events triggered other lines LER T. Liu, Oct. 99, L1 Strategy Some rejected bkg evts will still contribute to overall rate

Fully rejected bkg evts Some rejected bkg evts triggered other lines as well Run 9304 L1 pass thr only Fully rejected bkg evts L1 rate reduction~11% Total L1 rate reduction depends on other trigger lines T. Liu, Oct. 99, L1 Strategy Room for improvement --> better line combination

DOCAD algorithm: possible improvement Base line design: Require: 3/3 in the outer slices 2/3 in the inner slices If we require: 3/3 in ALL slices 70% bkg rejection! But 20% signal loss Due to cell ineff. More careful TSF LUT calibration is necessary T. Liu, Oct. 99, L1 Strategy

= Require 3/3 in ALL slices DOCAD algorithm: possible improvement  1 TSF can determine segment location with 1 mm resolution only for 4/4 patterns But 20% signal loss The resolution is degraded for 3/4 patterns: Due to cell ineff.  1 2 x x x x x = x x + x x x x 3/4 4/4 4/4 1 <  < 2 calibrating 3/4 patterns should help 70% bkg rejection! using the  information should help (baseline design ignored ) T. Liu, Oct. 99, L1 Strategy Currently 3/4 pattern LUT is derived from 4/4 patterns

The Drift Chamber ( DCH ) L1 Long term strategy: cut in Z using TSF fine position info from stereo superlayers? Cell size: 1.2 cm x 1.8 cm The Drift Chamber ( DCH ) 10 superlayers of 4 layers each Axial and stereo alternate T. Liu, Oct. 99, L1 Strategy

Stereo SLs --> Z Axial SLs --> DOCA DOCAZD Tough but possible ! L1 long-term strategy: Can we cut in Z using TSF position info from stereo SLs? Stereo SLs --> Z Axial SLs --> DOCA DOCAZD Close to IP in z Cosmic ray events In other words: move some L3 DCH algorithm upstream to L1 (cut in doca&z) Off IP in z Tough but possible ! T. Liu, Oct. 99, L1 Strategy What to expect? The answer is in the TSF data we already have

Stereo SLs --> Z Axial SLs --> DOCA DOCAZD L1 long-term strategy: Can we cut in Z using TSF position info from stereo SLs? Stereo SLs --> Z Axial SLs --> DOCA DOCAZD Current “trigger volume” Possible improved “trigger volume”?? What to expect? The answer is in the TSF data we already have! T. Liu, Oct. 99, L1 Strategy

Level 3 Filter Upon a L1 Accept ... DAQ Drift Chamber Upon a L1 Accept ... DAQ Using segments found by TSFs as seeds, fast algorithm applied to DCH data to further reject background... reduce the rate from 2 kHz to 100 hz. Level 3 Filter DAQ Fine position info for segments found for all superlayers Trigger data 24 Gbits/s Currently TSF provides fine position info for all SuperLayers to L3, only axial SLs info passed to PTD. T. Liu, Oct. 99, L1 Strategy Track Segment Finder (x24)

One possible scenario Level 3 Filter GLT DOCAZD ?? DAQ A,B Supercell Drift Chamber One possible scenario DAQ Level 3 Filter DAQ All track segments found Trigger data 24 Gbits/s A,B Supercell hits GLT DZ? Fine phi info for all(?) SLs DOCAZD ?? T. Liu, Oct. 99, L1 Strategy Track Segment Finder (x24)

L1 Strategy Summary Below and up to design luminosity In good shape, with some trigger line improvements (assume dataflow backplane build is successful & on time) 3 X 10**33 < luminosity < 1 X 10**34 Should be ok with DOCAD deployment Overall: Anders Borgland should be done with firmware change only (LBL new posdoc) Technical feasibility study in progress VHDL: Chris LeClerc Beyond 10**34 Possibility of cutting in Z using the unique capability of TSF Need to build new hardware for sure Can use existing TSF data to find out what to expect T. Liu, Oct. 99, L1 Strategy Careful TSF LUT calibration is essential !

LER T. Liu, Oct. 99, L1 Strategy HER

BABAR Trigger System ( L1 + L3 ) Design challenges Data taking environment at PEP-II: Beam crossings occur at 238 Mhz Design goal: May have severe beam background Event time must be determined High eff for ALL physics events Keep L1 rate below 2 kHz L1 Event time jitter < 1 s IFR Trigger Global L1 trigger (GLT) Trigger latency < 12 s EMC-EMT path Calorimeter Trigger Processor (TPB) Binary Track Linker(BLT) L1: hardware-based L3: software-based DCH-DCT path Track Segment Finder(TSF) Pt Discriminator (PTD) T. Liu, Oct. 99, L1 Strategy

T. Liu, Oct. 99, L1 Strategy

T. Liu, Oct. 99, L1 Strategy

Who trigged events without any track? HER 1U = 1 high P muon in backward IFR endcap T. Liu, Oct. 99, L1 Strategy

Run9304, L1 pass thr Trigger lines for events without any tracks T. Liu, Oct. 99, L1 Strategy

Who trigged LER? (+ 50% cosmic) T. Liu, Oct. 99, L1 Strategy D2*+ = B* & 1A & 1A’

Who trigged HER? (+1/4 cosmic) T. Liu, Oct. 99, L1 Strategy D2*+ = B* & 1A & 1A’

Run9304, L1 pass thr Number of tracks and trigger lines for run9304 T. Liu, Oct. 99, L1 Strategy Run9304, L1 pass thr

L1 Trigger Lines for Hadron Skim T. Liu, Oct. 99, L1 Strategy

The Drift Chamber ( DCH ) 10 superlayers of 4 layers each Axial and stereo alternate T. Liu, Oct. 99, L1 Strategy