D0 Muon System

1. D0 Muon System Sub-detectors Status PDTs Central Scintillation Counters MDTs Pixels Experience with On-line Data Quality Monitoring Summary Dmitri Denisov

2. Cross-sectional view of the D Run 2 detector. Forward MDT Layers C B A Pixel Counter Layers A B C PDT Chambers C B A Cosmic Cap Counters A- Counters CF North South Shielding Shielding EF EF CF Preshower Silicon Tracker 2T Solenoid Fiber Tracker Electronics Dmitri Denisov

3. PDTs – Proportinal Drift Tubes • PDTs is central muon tracking system • We have 94 PDTs total with typical size 2x4m2 • ~6,000 wires total in 10x4cm drift cells • Plus electronics to measure drift time (=muon coordinate) • Total number of disabled wires/channels is ~2% • PDT chambers are rather old (been built in late 80’s) • Have been substantially upgraded (HV, gas, electronics, etc.) for Run II • Currently known issues with PDTs are • High dark currents for some of A and B/C chambers • Causing high hits noises as well • Failures of front-end electronics (CB, Control Boards) typically during scraping • Radiation effects? • Known un-resolved issues with CB hardware and firmware • Cause mishandling of high multiplicity events • Lack of spare electronics boards and reliable ways of testing them (not on the working PDTs) Herman Haggerty is working on PDT wires During Run II upgrade Dmitri Denisov

4. Proportional Drift Tubes • What is not yet well under control with PDTs • Aging • Painful Run I experience • No well developed monitoring in Run II yet • Gas system • Monitoring of impurities and their effects on PDTs operation • Time-to-distance • Aging • Response to problems during operation • Team of experts in process of been formed • On-line efficiency monitoring • Problems with PDTs over last year • ~ 3 weeks of operation with bad front-end code November-December 2002 • Better testing of code before going on-line is needed • Efficiency cross checks using other(!) detectors • Not perfect T0s for first ~4 months in 2003 • Off-line correctable • PDT on-line timing monitoring is needed PDT Efficiency Plot for Typical Physics Run Dmitri Denisov

5. Central Scintillation Counters • ~1,000 scintillation counters in the central rapidity region • Used to trigger on events with muons • Reject backgrounds (cosmic, beam sprays, etc.) • Muon track reconstruction • Running stably • Number of non-working channels is in the 0.1% range • No known issues • Planned improvements • A-phi counters thresholds optimization • Monitoring of counters efficiency • Monitoring of counters aging • Front-end electronics boards improvements • Large voltage drop on a specific fuse creating “flaky” boards Cosmic Cap A-Phi Dmitri Denisov

6. Mini-Drift Tubes • MDTs is muon tracking detector in the forward rapidity region • 50,000 wires and electronics channels • Built for Run II • 1x1cm2 drift cell with maximum electron drift time of 60ns • Stable operation over last 2 years • Number of non-working channels is ~0.4% • ~0.2% are due to electronics boards (noise, failures, etc.) • ~0.2% are due to detectors (HV noise, broken wires, etc.) • A layer MDTs are operating for 2.5 years without single access • Space flight reliability! • Last changes to MDT operating parameters (delays, thresholds, etc.) • Autumn 2001 • No known issues • It takes considerable amount of efforts to keep such large system working stably • Power supplies/fuses replacements (more then 1000 fuses in the system!) • Noisy wires disabling • Planned improvements • Access to A layer during August shutdown • Minor gas leaks • Electronics repairs MDT A Layer Dmitri Denisov

7. Mini-Drift Tubes • On-line monitoring for MDTs is well developed and all issues have been quickly detected • Examine, alarms, monitoring GUIs • Noisy channels • Failure of detector elements, HV, electronics • In addition to daily monitoring by shifters • Daily checks by experts • Weekly experts checklists • About 20 pages of data • Periodic experts maintenance • During shutdowns MDT Coordinate resolution is ~0.7mm MDT Planes Efficiency Dmitri Denisov

8. Forward Trigger Counters (Pixels) • Designed and built for Run II • ~5,000 scintillation counters and electronics • Arranged in R-f geometry for triggering • 3 layers: A, B and C • Operating smoothly since beginning of Run II • Typical number of dead channels is ~0.1% • Last changes to operating parameters (trigger gate width) • Late 2001 • Stability of timing measurements • Intrinsic is ~0.2ns • Can see drift of accelerator clock by ~2-3ns over a year • Time resolution is well in agreement with expectation at ~1.8ns • Known problem • Reliability of VME power supplies in the hall • Radiation damage during scraping • About once per month – loosing ~8% of coverage during affected store • New supplies ordered, plan to replace all of them (~50% already replaced) within ~2 months C layer Pixels plane Dmitri Denisov

9. Forward Trigger Counters • On-line monitoring for Pixels is well developed and all problems have been easily detected • Examine, alarms, monitoring GUIs • Failure of detector elements, HV, electronics • In addition to daily monitoring by shifters • Daily checks by experts • Weekly experts checklists • About 10 pages of data • Periodic experts maintenance • During shutdowns 1 year timing stability Mean=0.24ns s=0.6ns On-line Efficiency Monitoring Pixels Timing Distributions Dmitri Denisov

10. On-line Muon Quality Monitoring and Operations • What works well • Check lists • Shifters/experts filling check list • Examine plots • Most of problems are easy to detect (see failed PDT in efficiency plot above) • Alarms • Most serious problems (HV trips, power supplies trips, etc.) are pausing physics runs • GUI (readout, RMIs, etc.) • Provide info about problems (crate our of synchronization, gas flow fluctuations, etc.) • Even “resolve” minor problems (readout GUI) • What could and should be improved • Understanding of PDTs • Even experts are having problems with some of the cases • Better monitoring for PDTs • On-line efficiency • Why fluctuating? • Normalized to tracks found in other sub-systems • Well defined and optimized list of alarms • Notes of what to do in the case of alarms to be added • Reliability of pixels VME crates power supplies • Reference plots for Examine • Availability of spare electronics boards • Better communication between Global Monitor, Off-line monitoring and Muon shifters/Experts • We need more dedicated groups/collaborators in order to resolve existing problems, develop better monitoring tools and support muon system operation! Dmitri Denisov

11. Summary • Muon system operating reasonably well over last year and there are no serious known problems affecting physics capabilities of the D0 detector • There is well defined plan of improvements • Reliability of the muon system elements • Monitoring tools • Better understanding of how detectors/electronics work • Especially PDTs • System is large and complex with over 100k channels of detectors and electronics • Groups of dedicated experts are working hard to keep system running stably • We do need extra help for long term operation and improvements in data quality • There are interesting new results already coming and expected to come based on D0 muon system • 100’s of thousands of J/Psi’s! • Close to 10k of Z’s • And coming… Opposite sign high Pt di-muon mass plot Dmitri Denisov