babar risks and mitigations

BABAR Risks and Mitigations

David B. MacFarlaneB Factory Operations

ReviewApril 26, 2006

April 26, 2006 BABAR Risks and Mitigations 2

Sources of risk

Installation and schedule risk associated with replacing barrel RPCs with LST moduleso Extensive discussion of planning and issues in Bill

Wisniewski’s talk

Radiation damage and occupancy in detector hardware systemso Extensive discussion for SVT in Bill Wisniewski’s talk;

background studies in Matt Weaver’s talk

Ability to maintain an open trigger for full physics potentialo Discussed here


Risks to the Detector

Radiation Damageo SVT sensors, readout electronics (S/N degradation, shorts)

• Replacements available for horizontal modules, but will not be installed based on risk/benefit analysis

• Remainder of detector will remain operational through at least 2008

o DCH damage to wires (Malter effect): lifetime well beyond 2008

o EMC damage to crystals (color centers): lifetime well beyond 2008

o Continuing to monitor damage• Have performed extensive irradiation studies,

understand limits of SVT very well• Maintain tight control of beam abort and injection

inhibits (relaxed to improve data collection efficiency and machine performance once understood)


Risks to the Detector

Data-taking inefficiency & dead-time o Services: system backups (chillers) (continuing)o DAQ: upgrade to online farm (replacement funded and in

planning)o Trigger: upgrade for z info (successfully deployed and operational

since the end of Run 4)o DCH: data transmission bottleneck (successfully deployed and

operational since February)• Understanding other possible bottlenecks, e.g., SVT, EMC• Additional tools: shielding & restrictive trigger & understanding

Machine Detector Interface Groupo Existed during BABAR construction & commissioningo Re-established with added scope in 2003

• New mandate includes working with accelerator team on machine background simulations, beam parameters at the collision point, instrumentation & analysis

o Addresses issues of extrapolation and modeling of backgrounds that contribute to radiation damage and data-taking inefficiencies


Trigger Rate Projections From the Trigger Group: need <140us

Actual experience in

2005 and 2006 has proven better than

extrapolation

Extrapolation prior to DCZ

deployment: will revisit this spring


Fiber Transfer Bottleneck

Pro

cess

ing

Tim

e

ROM (only 2 for EMC: endcap/barrel)

Eliminated by DCH readout

upgrade


Deadti

me (

%)

Trigger Rate (Hz)

Front-end Readout

(4 buffers)

DCH Feature

Extraction Bottleneck

Deadtime problem was foreseen in DAQ projections

Installed for Run5a

Factor 2 improvement

Installed for Run5b but not activated in October

Present DAQ limit seen in October

Phase II DCH upgrade

Phase I DCH upgrade

FEX code now installed and operational on DCH

endplate

Actual soft rise in deadtime somewhat faster than model predicts: under

investigation


Behavior of Fiber Bottleneck

Deadtime behavior on this plot is worse if L1 more “bursty” than Poisson (current evidence suggests not Poisson).

Current performance

equivalent to ~3 FE buffers: under

investigation


Possible Plan of Attack for Fiber SVT:

o Readout specific bad modules from both left and right. Factor of 2 gain? Might not work everywhere (especially for damaged modules?)

o Mask out small regions with high occupancyo Try running system at 60MHz (requires substantial new

effort, may not work)o Reduce occupancy with thresholds

Plan: Investigate 60MHz clock rate for data acquisition, thresholds, and masking

techniquesImpact: Should allow L1 rates up to 5Khz


FEX Bottleneck

140us

Eliminated by DCH readout

upgrade

Can be improved Challenging


Plan of Attack for FEX EMC FEX hard! Already a lot of work on this, not likely

to be substantially improved.o New CPUs won't work easily: mechanical, electrical, software

issues. significant work and money ($300K).o May be possible to pass EMC data to a small secondary farm, but

substantial work would be required to investigate and deploy DRC and SVT FEX relatively easy (don’t “do” anything)

but still have to be validated carefully. EMT FEX: Event “prescaling” deployed, with expected

improvement Currently SVT, EMT, GLT deadtime behavior not as

predicted and under investigation

Plan: Removing EMC FEX limit may be prohibitive at this point, although some ideas are under

considerationImpact: L1 rates could be limited to 5Khz


VME Bottleneck

140us

OverestimatedWill re-split this crate

Plan: May be possible to speed up EMC


L1 Trigger System


L1 Trigger Primitives (I)

DCT primitives:o BLT coarse rf tracks with no Z/tan/Pt info

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

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

o 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: o M20: strip energy sum MIP (>120MeV)

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

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

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

IFT primitive: o U3: coded pattern number for various 2 muon and 1 muon

barrel/endcap hit topologies


This configuration is used throughout 2001-2004 runs.

The ‘Beam/beam’ contribution can also be due to low angle Bhabha debris.

Feb/02


Possible L1 configuration improvements

Present DCZ trigger

Additional 1Zn track for some

lines


Possible L1 configuration improvements

Example of tighter DCZ configuration: Add a requirement for a loose ZPD track = 1Zn, with either Pt>+0.8GeV/c or Pt<-0.25GeV/c

Current DCZ Test case BB generic 100.0% 100.0% B-> + B->X 99.85% 99.85% B-> + B->X 100.0% 100.0% cc 99.98% 99.96% uds 98.92% 98.78% Bhabha 99.94% 99.94% 99.74% 99.68% 98.58% 98.35%

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

Reduces L1 trigger rate by 13% with no impact on physics

acceptance


Conclusions

Radiation damage to hardware systems carefully monitored and controlledo Except for a small angular range in horizontal plane of the

SVT, all systems will continue to perform through and beyond 2008

o Occupancies also result in modest impact on efficiency, under investigation and study

Approaching a number limits for daq systemo Removing fiber limit for SVT next goal, as well as resolving

small discrepancies in model performance vs datao EMC FEX would be a substantial challenge, possibly

representing a limit for L1 trigger rate at ~5kHzo L1 trigger investigations ongoing; should be sufficient

handles with new DCZ trigger elements to keep rate below 5kHz with little or no physics impact

babar risks and mitigations

Documents

dch damage

trigger group

emc damage

dch upgradephase

open trigger

data acquisition

dch upgradefex code

limits of svt