BABAR Risks and Mitigations

1. BABAR Risks and Mitigations David B. MacFarlaneB Factory Operations Review April 26, 2006

2. Sources of risk • Installation and schedule risk associated with replacing barrel RPCs with LST modules • Extensive discussion of planning and issues in Bill Wisniewski’s talk • Radiation damage and occupancy in detector hardware systems • 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 potential • Discussed here BABAR Risks and Mitigations

3. Risks to the Detector • Radiation Damage • 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 • DCH damage to wires (Malter effect): lifetime well beyond 2008 • EMC damage to crystals (color centers): lifetime well beyond 2008 • 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) BABAR Risks and Mitigations

4. Risks to the Detector • Data-taking inefficiency & dead-time • Services: system backups (chillers) (continuing) • DAQ: upgrade to online farm (replacement funded and in planning) • Trigger: upgrade for z info (successfully deployed and operational since the end of Run 4) • 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 Group • Existed during BABAR construction & commissioning • 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 • Addresses issues of extrapolation and modeling of backgrounds that contribute to radiation damage and data-taking inefficiencies BABAR Risks and Mitigations

5. Trigger Rate Projections • From the Trigger Group: need <140us Extrapolation prior to DCZ deployment: will revisit this spring Actual experience in 2005 and 2006 has proven better than extrapolation BABAR Risks and Mitigations

6. Eliminated by DCH readout upgrade Fiber Transfer Bottleneck Processing Time ROM (only 2 for EMC: endcap/barrel) BABAR Risks and Mitigations

7. Present DAQ limit seen in October Deadtime problem was foreseen in DAQ projections Phase I DCH upgrade Installed for Run5a Factor 2 improvement Installed for Run5b but not activated in October DCH Feature Extraction Bottleneck Deadtime (%) Phase II DCH upgrade FEX code now installed and operational on DCH endplate Actual soft rise in deadtime somewhat faster than model predicts: under investigation Front-end Readout (4 buffers) Trigger Rate (Hz) BABAR Risks and Mitigations

8. Behavior of Fiber Bottleneck Current performance equivalent to ~3 FE buffers: under investigation Deadtime behavior on this plot is worse if L1 more “bursty” than Poisson (current evidence suggests not Poisson). BABAR Risks and Mitigations

9. Possible Plan of Attack for Fiber • SVT: • Readout specific bad modules from both left and right. Factor of 2 gain? Might not work everywhere (especially for damaged modules?) • Mask out small regions with high occupancy • Try running system at 60MHz (requires substantial new effort, may not work) • Reduce occupancy with thresholds Plan: Investigate 60MHz clock rate for data acquisition, thresholds, and masking techniques Impact: Should allow L1 rates up to 5Khz BABAR Risks and Mitigations

10. Eliminated by DCH readout upgrade 140us FEX Bottleneck Challenging Can be improved BABAR Risks and Mitigations

11. Plan of Attack for FEX • EMC FEX hard! Already a lot of work on this, not likely to be substantially improved. • New CPUs won't work easily: mechanical, electrical, software issues. significant work and money ($300K). • 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 consideration Impact: L1 rates could be limited to 5Khz BABAR Risks and Mitigations

12. 140us VME Bottleneck Overestimated Will re-split this crate Plan: May be possible to speed up EMC BABAR Risks and Mitigations

13. L1 Trigger System BABAR Risks and Mitigations

14. L1 Trigger Primitives (I) • DCT primitives: • BLT coarse rf tracks with no Z/tanl/Pt info • A16: long track reaching SL10 (Pt>180MeV) • B16: short track reaching SL5 (Pt>120MeV) • ZPD 3D tracks with Z/tanl/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) BABAR Risks and Mitigations

15. L1 Trigger Primitives (II) • EMT primitives: • M20: f strip energy sum MIP (>120MeV) • G20: f strip energy sum medium E (>300MeV) • E20: f 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 BABAR Risks and Mitigations

16. This configuration is used throughout 2001-2004 runs. The ‘Beam/beam’ contribution can also be due to low angle Bhabha debris. Feb/02 BABAR Risks and Mitigations

17. Possible L1 configuration improvements Present DCZ trigger Additional 1Zn track for some lines BABAR Risks and Mitigations

18. 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 DCZTest case BB generic 100.0% 100.0% B->p0p0 + B->X 99.85% 99.85% B->tn+ B->X 100.0% 100.0% cc 99.98% 99.96% uds 98.92% 98.78% Bhabha 99.94% 99.94% mm 99.74% 99.68% tt 98.58% 98.35% (Hadronic final states: all events Leptonic final states: fiducial events) Possible L1 configuration improvements Reduces L1 trigger rate by 13% with no impact on physics acceptance BABAR Risks and Mitigations

19. Conclusions • Radiation damage to hardware systems carefully monitored and controlled • Except for a small angular range in horizontal plane of the SVT, all systems will continue to perform through and beyond 2008 • Occupancies also result in modest impact on efficiency, under investigation and study • Approaching a number limits for daq system • Removing fiber limit for SVT next goal, as well as resolving small discrepancies in model performance vs data • EMC FEX would be a substantial challenge, possibly representing a limit for L1 trigger rate at ~5kHz • 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