L1 Trigger Strategy

Ted Liu, July 5,00, idea on Ztrigger

L1 Trigger Strategy

• L1 Trigger Requirements and Trigger Lines• L1 Trigger performance• Background Study• Improving Performance: near-term strategy • Future Prospect: long-term strategy• summary

Ted Liu, Lawrence Berkeley Lab (for the trigger group)


Trigger Line Definition/Convention

DCT Objects:

A: long track reaching SL10, Pt ~180 MeV

B: short track reaching SL5, Pt ~120 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

B*,M*...* means back-to-back objects(>120 )D2 = 2B&1A, D2* = B*&1AD2*+ = B*&1A&1A’ , A+ = A&A’

o


Trigger Lines for Hadronic Events

B Physics

Continuum

Pure DCT

Pure EMT

DCT + EMT

CP Channels: high eff.

Non-CP channels: high + precise eff.

Requirements:

High & precise eff.for background sub.

orthogonal linesredundant linesrecord all trigger DAQ dataprescaled lines

Strategy for eff. Measurements:

run9304


Use orthogonal DCT-EMT lines to study eff.

Total eff for hadron skim: (EMT OR DCT) > 99.3%

From Su Dong


Trigger Lines for non-physics Events

Luminosity, calibration:2-prong ee,High + precise eff.

Pure DCT

Pure EMT

DCT + EMT

Requirements:

Calibration, beam monitor:1-prong ee,

Background&Trigger studies

Background monitoring

only

run9304


Trigger Lines for and 2 Events

Physics

Pure DCT

Pure EMT

DCT + EMT

Rare & Asy.: high eff.

Branch Ratios: precise eff.

Requirements:

precise eff.

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.

Shortcomings:

2 Physics

Expected @ high background rate, will try to improve…add 2BM+1AM, lower Pt cut?


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

...


HERLERSingle beam

L1 pass thr.events

Z distribution

LER

HER

From S. Petrak


HERLER

Single beam

L1 pass thr. events

x-z view

Many tracks from beampipe: off Z --> off IP in x-y

LER

HER


Trigger data

Fine position data forsegments found foraxial SLs

Drift Chamber

Track Segment Finder (x24)DOCAD

24 Gbits/s

Coarse datafor all supercellhits

Binary Track Linker (BLT x1)

PT Discriminator

PTD (x8)

GLT

A, B

A’

16

16

DCT Trigger Hardware

New idea

(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 nsspatial resolution ~ 1 mm used for track Pt Discrimination

Use 24 TSF modules

(2) send segment patterns to the DAQ system for use in Level 3 ...

(1) send segment patterns downstream forL1 trigger decision making

Upon a L1 accept:

Track Segment Finder




x

x A10 seed

IP

SL7

SL4

SL1

Pt threshold (800MeV)

Current PTD algorithm

x

x

SL7

SL4

SL1

IP

New DOCAD algorithm

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

4 hits on one track with ~1mm,should be able to tell whether the track is from IP

(baseline design: simple algo.)

800MeV850MeV900MeV1 GeV


Apply DOCAD algorithm to TSF data Hadron skim: signal

LER single beam run: background

PTD on

DOCAD on

PTD on

DOCAD on

Background rejection: 40%

Effect on Signal:

Effect on Background:

Use hadron skim (~10% bkg)

~ 4% loss at turn on

Use single beam runL1 pass thr events

40% rejection on A’ linewith simple algorithm

Max Pt in the event

The goal here is not to find thebest algorithm possible, but onewhich is easy to be implementedand with good performance


DOCAD algorithm: possible improvement Require 3/3 in ALL slices

70% bkg rejection!

But 20% signal loss

Due to cell ineff.

TSF can determine segment location with 1 mm resolutiononly for 4/4 patterns

The resolution is degraded for 3/4 patterns:

=xxx

xxx

x

xx

xx

3/4 4/4 4/4

1 2

1 < < 2

calibrating 3/4 patterns should help

Currently 3/4 pattern LUT is derived from 4/4 patterns

+

using the information should help(baseline design ignored )


The Drift Chamber ( DCH )

10 superlayers of 4 layers each

Axial and stereo alternate

Cell size: 1.2 cm x 1.8 cm

L1 Long term strategy: cut in Z using TSF fine position info from stereo superlayers?


L1 long-term strategy:

Can we cut in Z using TSF position info from stereo SLs?

Stereo SLs --> Z Axial SLs --> DOCA

DOCAZD

Cosmic ray events

Close to IP in z

Off IP in z

In other words:move some L3 DCH algorithmupstream to L1 (cut in doca&z)

Tough but possible !

What to expect? The answer is in the TSF data we already have


B1B1

Track z distributionfor L1 passthroughevents

LERHER

Lost particle interact with beampipe flange

due to a step in the synchrotron mask

real collision


40~50 or so slices in theta

~ 2 cm in z for SL2

TSF phi resolution ~ 1 mm Z resolution ~ 2 cm

Off Z trackBasic idea (~16 new DOCAZ boards in phi)


L1 long-term strategy:

Can we cut in Z using TSF position info from stereo SLs?

Stereo SLs --> Z Axial SLs --> DOCA

DOCAZD

What to expect? The answer is in the TSF data we already have!

Current“triggervolume”

Possible improved “trigger volume”??


Trigger data

DAQFine position info for segments found for allsuperlayers

Drift Chamber

DAQ

Level 3 Filter

Track Segment Finder (x24)

Upon a L1 Accept ...

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.

Currently TSF provides fine position infofor all SuperLayers to L3, only axial SLsinfo passed to PTD.

24 Gbits/s


Trigger data

DAQAll track segments found

Drift Chamber

DAQ

Level 3 Filter

Track Segment Finder (x24)

24 Gbits/s

DOCAZD ??

GLT

A,B

DZ?Fine phi infofor all(?) SLs

Supercellhits

One possible scenario

Ted Liu, July 5,00, idea on Ztrigger HER

LER




The Drift Chamber ( DCH )

10 superlayers of 4 layers each

Axial and stereo alternate

Documents

L1 Trigger Strategy