Dec/02/04 Su DongCaltech Trigger/DAQ/Online workshop1 Level 1 Trigger: Introduction L1 trigger objects and strategy Implementation features L1 composition

Dec/02/04 Su Dong Caltech Trigger/DAQ/Online workshop 1

Level 1 Trigger: Introduction

• L1 trigger objects and strategy

• Implementation features

• L1 composition and rate projection

Su Dong


Trigger Requirements and General

Strategy The basic requirement of the trigger system is to select Interesting physics events with high, stable and well understood efficiency.

Some implementation features:• Trigger lines mostly defined by generic topology

(2,3,4 particles etc.), not by specific physics source.• Deploy orthogonal triggers using pure DCH or pure

EMC triggers with high efficiency for affordable topologies.

stability and efficiency measurability.• Built in tolerance for detector inefficiencies:

– Accept 3 out of 4 hits for track segment finding in a superlayer

– Allow missing segments in L1 and L3 track triggers – Allow at least one signal particle is allowed to miss

DCH or EMC trigger, whenever possible.


L1 Trigger System


L1 Trigger Primitives (I)

• DCT primitives:BLT coarse rtracks with no Z/tan/Pt info

– A16: long track reaching SL10 (Pt>180MeV)

– B16: short track reaching SL5 (Pt>120MeV)

ZPD 3D tracks with Z/tan/Pt info reaching SL7

– Z16: standard Z track (|Z|<12cm, |Pt|>200 MeV)

– Zt8: tight Z cut track (|Z|<10cm, |Pt|>200 MeV)

– Z’8: high Pt track (|Z|<15cm, |Pt|>800 MeV)

– Zk4: moderate Pt cut (|Z|<10cm, |Pt|>350 MeV)


L1 Trigger Primitives (II)

• EMT primitives: – M20: strip energy sum MIP (>120MeV)

– G20: strip energy sum medium E (>300MeV)

– E20: strip energy sum high E (>800MeV)

– Y10: Backward barrel high E (>1 GeV)

• IFT primitive: – U3: coded pattern number for various 2

muon and 1 muon barrel/endcap hit topologies


L1 Trigger Features (I)• PEP-II beam essentially continuous so that L1

trigger also operates in `DC’ mode in conjunction with fully pipelined subdetector frontend electronics.

• There is no fast trigger detector element such as TOF but still get L1 time resolution of ~50ns.

• Subsystem readout work on raw waveform to calculate pulse height => decouple trigger timing from pulse heights. However, there are pathological effects in frontend electronics input to trigger or vulnerable trigger settings which can introduce gross timing shifts. Careful testing is required for changes with timing consequences.


Ghost retriggering events (from 2000)

Due to EMC electronics glitch during a ramping down pulse


L1 Trigger Features (II)

• Low multiplicity triggers such as 1B can sometimes saturate at high background conditions so that e.g. 2B is on, but 1B may appear to be off due to lack of off-

>on transition. • GLT trigger lines are currently optimized

for best mean time alignment between lines. If we were to deliberately delay L1 as late as possible to minimize SVT ‘background hit poisoning’, we may need to try optimizing for best late edge alignment.


L1 Trigger Line Naming Conventions

• 3B&2A means B>3 and A>2 • M* means 2 M hits back to back • EM* means M and E hits back to back • A+ means A>1 & A’>1 • D2 means B>2 & A>1 (short hand 2 trk trg) • BM means B matched by M in same location

For counting distinct objects from the maps:• Normal objects (B,A,M,E etc.) are separated by

more than 1 f bin: 22.5o for DCT tracks, 18o for EMT hits.

• Back to back angles cuts for B*,M*,EM* ~120o. • DCT/EMT match objects BM ~90o apart.


This configuration

is used throughout

2001-2004 runs.

The ‘Beam/beam’

contribution can

also be due to low

angle Bhabha

debris.

Feb/02


L1 Trigger Efficiency 2001-2004 old DCT configuration: Pure DCT Pure EMT All L1

lines BB generic 99.1% 99.8% >99.9% B-> + B->X 79.7% 99.2% 99.8% B-> + B->X 92.2% 95.5% 99.7% cc 95.3% 98.8% 99.9% uds 90.6% 95.6% 98.2% Bhabha 98.9% 99.2% >99.9% 99.1% - 99.6% 80.6% 77.6% 94.5%

( Hadronic final states: all events Leptonic final states: fiducial events)


L1 Rate ProjectionFeb/02 Background runresult suggestPossible model:

L1 Rate (Hz) = 125 (cosmic)

+ 50*ILER(A)

+ 190*IHER(A)

+ 180*I2HER(A)

+ 70*L/1033

+ 100*ILER*IHER

at good conditions


Checking L1 Rate Projection

Derived background

L1 rate compared to prediction:

>2*backgr 24% >3*backgr 4.6% >4*backgr 2.2%

Use prediction with caution !


L1 Rate Extrapolations (Jan/04)


L1 Rate Extrapolations (Jan/04)

Model-2: + 100*Iher*I2ler + 100*L


Can we get more reduction outof DCZ ?


Backup Slides


L1 Trigger Rate Growth vs Trigger Types


New L1 Rate Extrapolations (II)

Model-1: + 50*Iher*Iler + 120*Iher*I2ler + 70*L


HER background characteristics


Lumi vs beam current

Documents

Dec/02/04 Su DongCaltech Trigger/DAQ/Online workshop1 Level 1 Trigger: Introduction L1 trigger objects and strategy Implementation features L1 composition