scifi trigger review: physics goals and algorithms kin yip, fermilab l1 trigger review, jan. 22,...

DD SciFi Trigger Review:SciFi Trigger Review:

Physics Goals and Physics Goals and

AlgorithmsAlgorithms

Kin Yip, Fermilab

L1 Trigger Review, Jan. 22, 1999

Physics Ingredients Min. PT

CFT Efficiencies and Occupancies Simulation involved Algorithms (VHDL coding etc.)

January 22, 1999SciFi L1 Trigger Review

2DD• LAFEX/CBPF, Rio de Janeiro,

Brazil – Mario Vaz - CBPF/LAFEX

DEL/UFRJ• University of California/Davis

– Sudhindra Mani• Fermilab

– John Anderson,– Linda Bagby,– Fred Borcherding, – Stefan Grünendahl,– Dave Huffman, – Marvin Johnson, – Jamieson Olsen,– Manuel Martin,– Mike Matulik, – Pat Sheahan,– Kin Yip

The Fiber Tracker L1 Trigger The Fiber Tracker L1 Trigger GroupGroup


3DD Tevatron ImpactTevatron Impact

Impact on DØ

– Integrated LL rad damage in tracking chambers replace tracker

– Shorter bunch crossing interval avoid pileup electronics pipeline, faster trigger

– higher rate need higher rejections (at every trigger level)

Description Run I Run II

Luminosity (0.5-2.0) 1031

cm-2 sec-1(0.8-2.0) 1032

cm-2 sec-1

Energy 1.8 TeV 2.0 TeV

Bunch Spacing 3500 nsec 396 → 132 nsec

Lum. to tape 120 pb-1 2000 pb-1


4DD Physics GoalsPhysics Goals

• Precision Tests of the Standard Model – precision measurements (top mass, W mass, ...)

• Constrain the Higgs Boson Mass

– improvements to B physics capabilities

– (Bs mixing, CP violation, …)

– QCD with W, Z, photon

• Extend the Discovery Reach– More data samples allow significant increases in

the reach for SUSY, leptoquarks, W’,Z’,anomalous couplings, intermediate mass Higgs …

• All these will benefit from the CFT tracking trigger to help trigger on electrons/muons etc.; • STT and Muon Trigger rely on the CFT track seeds;• PreShower uses CFT tracks to identify electrons/photons.


5DD Minimum PMinimum PT T & Number of & Number of

EquationsEquations

• Minimum PT is set to be 1.5 GeV/c :

• to reasonably cover B physics (etc.) spectrum;• J/ good for calibration;

• tracks with lower PT would not pass thro’ calorimeter.

Plot

• Due to 1.5 GeV and the fact that we use 8 CFT layers for

trigger, the total no. of equations (allowed trajectories) in

each CFT sector 16000 ( with the present geometry )

Plot


6DD Typical B physics Typical B physics spectrumspectrum


7DD # of Equations vs # of Equations vs PPTT/offset/offset

NPT ~ 1/PT


8DD Tracking Trigger Tracking Trigger OverviewOverview

Trigger response for Z ee with 4 min.bias (1) Fiber light signals electronic signals

(2) Feed all axial fibers into logic gates/cells in

Programmable Logical Devices

(3) Fiber hit pattern recognition to look for tracks

consistent with momentum PT > 1.5 GeV/c

(4) Send out the track information to outside L1 CFT

VLPC


9DD Tracking AlgorithmTracking Algorithm

• There are 80 sectors in CFT, each subtending 4.5;

• Seamless tracking requires fiber sharing between nearest sectors; • Tracks with PT1.5 GeV are contained within 2 neighbor sectors;

• Fiber hits are transmitted from a sector to either side for track matching.

CFTSector 1 CFT

Sector 2

TrackSector boundary

No crack in tracking


10DD Tracking Algorithm Tracking Algorithm (cont.)(cont.)

= 0

j

j

j -1

+

Inner Singlet

Outer Singlet

Doublet

Doublet Algorithm :

• Form “doublet bin” by combining individual fiber hits in the inner and outer singlet layers.

• “Or” combines inner and outer layers; “AND” with the “NOT” makes the bins non-overlapping.

Doublet[j] ={ NOT(Outer[j]) AND INNER[j] } OR Outer[j+1]

It has been shown that doublet layer efficiency > 99.5%.



• Basic algorithm : matching hit patterns in all 8 layers with a pre-programmed set of “equations” ;

• Compute trajectories ( equations ) analytically for all possible tracks for

momentum PT 1.5 GeV and download them into PLD’s on the FE board;

• based on the fact PT magnetic field strength (2T) radius of curvature;

• equation - a set of 8 fiber indices;

• There are about >16000 equations for each sector ;

• Algorithm uses 8 out of 8 doublet layers;• with an option to require only 7 out of 8 layers at highest PT later in the run;

• Use the outermost layer (8th layer, H layer) as the anchor layer (reference layer)

where there are 44 fibers in each sector.


12DD Monte Carlo Monte Carlo SimulationSimulation

• Monte Carlo simulation studies using the D upgrade configuration have been done in various physics samples.• Single electron/muon samples are used to tune the efficiency of the trigger algorithm. For PT >3 GeV, efficiencies:

•>97% for muons and •~95% for electrons,

limited by multiple scattering and various radiation effects.

• A working (though preliminary) C++ code in Run II framework is available.

• Plot shows how the CFT trigger efficiencies when different sets of equations (belonging to certain PT thresholds) are used.


13DD Track BinningTrack Binning• PT binning yields sharper turn-on than offset binningoffset = [(projection of H layer fiber hit on A layer) - A layer hit fiber] in units of fibers

} 50%

} 20%

}15%

}15%

Eqn #



• From Monte Carlo simulation studies, we can limit ourselves by allowing only 2

tracks in each H layer fiber and 6 tracks in each of the 4 PT thresholds in each sector

virtually without losing any tracking efficiency.

• Need 2 tracks because of extra hits at high luminosity which create a fake track

(7 points on original track and 1 fake).• Fake track can be higher or lower in PT than the real one.

• ~90% — only 1 track passes through a fiber ;

• ~10% — 2 tracks pass through a fiber.

• Only 48 tracks per broadcaster.

1 track2 tracks

ttbar6.8%0.3%

Z bb_bar10.9%0.4%

Inefficiencies


15DD OccupancyOccupancy

Using samples with 8 interactions,average no. of tracks :

15 per event 0.19 / sector per event

non-overlapped : only 8.8 per event or 0.11/sector per event

For samples with 2 interactions, applying (7 out of 8 ) would increase the number of tracks by ~ 67%.



• Basic Algorithm is to match 8 fiber hits in 8 layers (A,B…,H) with the pre-programmed equations in PLD’s;

• Use PLD’s (each with ~ 100,000 logic gates) to handle the trigger logic;

• Use HDL (Hardware Description Language) to implement the tracking logic like:

T1013172227323945 = A[10] AND B[13] AND C[17] AND D[22] AND E[27] AND F[32] AND G[39] AND H[45]

( There are >16000 of them in each sector ! )



• Put all equations in ~4 PLD’s according to the PT threshold ;

• The trigger codes in the PLD can be reprogrammed many times but the I/O pins to each PLD’s are fixed ;

• All fiber signals in a sector ( with some from the neighbor sectors ) would be feeded into every PLD so that each PLD can handle tracks with the entire PT range ; gives us flexibility to change equations with different PT in a PLD ;

• We allow each PLD to have at most 2 threshold ranges of PT only.



• Input fiber patterns are matched with the equations tracks at certain (PT,) bin;• A matrix of PT (H fiber position) :

PT

• Scan the matrix “horizontally” in groups and put in priority encoder which outputs the indices of PT bins with the highest priority;1-D list of indices and concatenated in a binary tree structure down to a list of 6 (tracks with the highest PT) in each PT threshold; A mixture of parallel/serial modes to reduce latency while keeping resources low.

0 1 2 3 4 5 6 7 8 9 10 111 0 0 1 0 0 0 0 0 0 0 ...2 0 1 0 0 0 0 1 0 0 1 …3 0 1 1 0 0 0 0 0 0 0 …4 0 0 0 0 0 0 0 0 0 0 …5 0 0 0 0 0 0 0 0 0 0 …6 1 0 0 1 0 0 0 0 0 1 …7 1 0 1 0 0 0 0 1 0 0 …… … … … … … … … … … … …


19DD Test ResultTest Result

Testing Result:•Algorithm and timing have been tested in the vendor software simulation and implemented in a trigger test board with PLD’s;• The measured timing in the real PLD’s agrees very well with the simulation and the result of the trigger logic is what is expected.

Tracking logic completed < 85 ns

simulationresult


20DD OutputOutput

Output:CFT track information are formatted in the FE board, combining cluster information from Central Preshower (L1);17 terms -- number of tracks in each of 4 PT thresholds, track/cluster

matches, total number of hits etc. are sent via a fast serial link to L1 trigger framework for a final L1 decision;

A max. of 6 highest PT tracks are sent to L1 muon trigger (within 800 ns);

Up to 24 tracks are pipelined for later readout to L2 trigger;Leaving FE boards, all available CFT tracks are selected and combined into 6 global lists of up to 48 tracks each, which are track seeds for L2 trigger.


21DDTerm Number Description of Term Term_16 . # of CFT fiber hitsTerm_15 CFT above Highest Pt ThresholdTerm_14 CFT above High Pt ThresholdTerm_13 CFT above Medium Pt ThresholdTerm_12 CFT above Low Pt ThresholdTerm_11 CFT/CPS above Highest Pt ThresholdTerm_10 CFT/CPS above High Pt ThresholdTerm_9 CFT/CPS above Medium Pt ThresholdTerm_8 CFT/CPS above Low Pt ThresholdTerm_7 isolated CFT above Highest Pt ThresholdTerm_6 isolated CFT above High Pt ThresholdTerm_5 isolated CFT above Medium Pt ThresholdTerm_4 isolated CFT above Low Pt ThresholdTerm_3 isolated CFT/CPS above Highest Pt ThresholdTerm_2 isolated CFT/CPS above High Pt ThresholdTerm_1 isolated CFT/CPS above Medium Pt ThresholdTerm_0 isolated CFT/CPS above Low Pt Threshold

Table. The definition, version 1.0, of the AND-OR terms from the L1 CFTTM.

Trigger termsTrigger terms


22DD SummarySummary

• Reasonable algorithms/restrictions on the L1 CFT trigger system;

• New technology such as VLPC & trigger logic in PLD’s meet:– Timing constraints

• allows feeding of L1 info to other detectors (muon & preshower)

– Flexibility• allows for adaptable thresholds/PT bins and changing equations

• Monte Carlo simulation in various physics samples have been performed to verify the trigger algorithm.


23DD

The End !!!


24DD Trigger SchematicTrigger Schematic

5-10 kHz128 bits

1000 Hz128 bits

20 Hz

L2100s

L14.2 s

L3 100 ms

50 nodes

Framework

7.6 Mhz, 132 ns crossing times

Accommodate : L=2x1032cm-2 s-1 & Bunch Crossings 132 ns

Maintain Run I e jet acceptance

Deadtime: <5%


25DD The DetectorThe Detector

The DØ upgrade builds upon the strengths of the existing detector (excellent calorimetry, muon coverage) and augments it with a high resolution Silicon/Scintillating Fiber tracker.

•calorimeter: replacement of preamps/shapers

•muon system: –replacement of muon chamber readout electronics

–Iarocci drift tubes replace forward muon chambers

–central and forward scintillator pixel layers enhance trigger capability.

•DAQ & trigger: add track and vertex triggering, add buffering, add processing power

•central tracker: –2 T supraconducting coil inside r=70 cm calorimeter bore

–lead/scintillator preshower detector with fiber/VLPC readout

–16 layer SciFi/VLPC tracker (80k channels)

–4 barrel / 16 disk Silicon tracker (1M channels)

•forward tracker/preshower: scintillator cells with fiber/VLPC readout


26DD VVisibleisible LLightight P Photonhoton C Countersounters

Passage of charged tracks produces light in scintillating fibers;

VLPC converts the light produced to electronic signals which are then transferred to the Front End (FE) board;

On the FE board, signals are digitized and discriminated by the Silicon Vertex and custom (SIFT) chips;

Signals are further latched into the PLD’s

(Programmable Logical Devices) on the FE

board to perform track finding logic.

Scintillating Fiber Optical Connector

Waveguide Fiber

Mirror

Photodetector Cassette Electrical Signal Out

Cryostat

VLPC


27DD System OverviewSystem Overview

• L1 System overview:– Front End Board (on cassette)

• VLPC signal discrimination• track pattern matching• track sorting & list building per

4.5 sector

– Receiver & Concentrator system (two crates)

• list building per octant (L1)• list building per sextant (L2)• L1-CFTTM and L2pp links

– L1 CFT Trigger Manager• forms trigger (‘and/or’) terms

for L1

CFTFE

kj

CFTL1

RC

L1Muon

L2CFTpp

L2STTpp

80 boards

2 crates

96 links

L1CFTTM

80 links

Passive Splitter

CFT_L1v3

copper

copper

copper

glass

L1CN

L2CN

4 boards

2 boards

2 boards

L2CN2 boards

CFTL1

L2PSpp

CFTCNSystem

L1 AMCC Links Copper - 1Gbit/sL2 G-link glass - 1Gbit/s


28DD Trigger RatesTrigger Rates

Using minbias events of 2 interactions:

7 out 8 in (A & B layers)

~5% increase in the trigger rate.

8 out of 8 ( from Bornali )


29DD Truncation schemesTruncation schemes


30DD DØ TrackingDØ Tracking

calorimeter cryostat

1.1

1.7

1.3 m

50

cm

Solenoid 2 Tesla superconducting

Central Fiber Tracker (CFT)– 16 doublet layers of Sci-Fi ribbon

• 8 axial (parallel to the z-axis) TRIGGER• 8 stereo(2o pitch), not used in TRIGGER

– 76,800 830 m fibers (multiclad)– coverage: 20<r<52cm, polar angle to ~22– In the radial plane, CFT is divided into 80

sectors (4.5)

• Silicon Tracker

• Preshowers• Central

• Forward

z-axis

scifi trigger review: physics goals and algorithms kin yip, fermilab l1 trigger review, jan. 22,...

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