The Performance of the Outer Tracker Detector at LHCb

1. The Performance of the Outer Tracker Detector at LHCb Barbara Storaci on behalf of the OT group

2. The mission Excellent mass resolution High tracking performace High Performance at the tracking detector (Andreas Jaeger’s talk) Precise Alignment (Raphael Marki’s talk) 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

3. LHCb SiTracker: (Mark Tobin’s talk) VELO: (Alexander Leflat’s talk) Outer Tracker : This Talk 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

4. OT: the detector • Drift Chambers detector based on straw tube technology: • Anode wire at 1550 V • Cathode straw connected to ground • Gas MixtureAr/CO2/O2 (70/28.5/1.5) Straw tubes packed in double-layered modules S2 S3 Type F S1 2400 mm • 3 stations for each side • Each station 4 layers (central layers tilted by ± 5°) 2900 mm 3070 mm 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

5. OT: the readout Data Fiber TFC & ECS LV HV • Readout Electronics hosted in aluminumframes installed at both ends of the detector (FE-box). • HV distribution • Preamplification and discrimination (ASDBLR) • Time to Digitalconvertion (OTIS) (TDC has to operate synchronous with 40MHz bunch crossing clock) • Data serialization for optical transmission (GOL) GOL/AUX OTIS ASDBLR 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

6. Quality assurance Quality Assurance during production: • Wire tension • Dark current • Wire pitch Quality Assurance after production: • Gas Tightness, Dark current • detector responseto 90Srβ-source Full scan (every cm2) of all OT modules Excellent uniformity of the response for all modules Module Classification (1st choice, 2nd choice, etc.) based on: • Dead channels: in general disconnected shorts (0.6‰) • “Noisy” Channels: high dark current (0.7‰), often “cured” after HV training) 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

7. Nasty Surprise: Ageing Ratio Plot: Iafter/Ibefore Peculiar characteristics: • Gas flow dependence: • most of the damage upstream the source • half-moon shape • Intensity dependence: • Maximum damage NOT at the highest intensity Gas flow Irradiated with a 2 mCi90Sr source 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

8. Nasty Surprise: Ageing Ratio Plot: Iafter/Ibefore Peculiar characteristics: • Gas flow dependence: • most of the damage upstream the source, • half-moon shape • Intensity dependence: • Maximum damage places NOT at the highest intensity Gas flow Irradiated with a 2 mCi90Sr source CULPRIT AY103-1 AY103 C16H22O4 Supplier produced the glue with a different plastifier: same mechanical properties… but AY103-1 causes ageing!!! C16H20 • diisopropyl-naphthalene dibutyl phthalate 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

9. Ageing Monitoring System • System in Situ: • Irradiation with 90Sr sources (74MBq) • Current read every centimeter • Scanning source: 2 90Sr sources (74MBq) • Can be used only during technical stop • Laboratory System: • Irradiation of a 6x6 cm2 area with 2mCi 90Sr source • Current read every centimeter • Scanning source: 20mCi 90Sr source 2 90Sr sources Scanning Frame Current-meter connectors Safety garage

10. Living with ageing • Outgassing: • Flushing • Heating • Addition of Oxygen to the gas mixture: • Production of ozone • HV training: • Induce high current in the module • Typical currents: • 10 μA per straw at 1900V Wire with carbon deposit 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

11. Recovery and Prevention: HV training • The HV training procedure: • Reset of the gain value • Prevent from further ageing (up to a certain dose) • From optical and SEM inspection: • Deposit removed • Wire undamaged Before training (previous damages clearly visible) recovery immunity After 15h training at 1900V in situ (only wires 33-64) 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

12. Threshold Scan with beam • Error function (assuming gaussian noise) to describe hit-efficiency vs threshold • Point at 50% of efficiency: half-efficiency point (HEP) • Variation of the HEP sign of gain loss (ageing) • PROCEDURE: • 1 scan every 200 pb-1 • Ten threshold for 12 layers (full detector) • 150000 events per step No gain loss beyond 10% observed yet

13. Readout Monitoring

14. Online-offline calibration software • Noise Threshold Scan: • Identifying channels that have an “abnormal” level of noise 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

15. Online-offline calibration software Noise level for the full detector <8*10-4 at working threshold • Noise Threshold Scan: • Identifying channels that have an “abnormal” level of noise 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

16. Online-offline calibration software Noise level for the full detector <8*10-4 at working threshold • Noise Threshold Scan: • Identifying channels that have an “abnormal” level of noise • Threshold Scan: • Identifying dead channels, gain deteriorating effects, etc. 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

17. Online-offline calibration software Noise level for the full detector <8*10-4 at working threshold • Noise Threshold Scan: • Identifying channels that have an “abnormal” level of noise • Threshold Scan: • Identifying dead channels, gain deteriorating effects, etc. • Delay Scan: • Identifying defects in the timing of the OT channels (offsets,non-linearities etc.) 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

18. Online-offline calibration software Noise level for the full detector <8*10-4 at working threshold • Noise Threshold Scan: • Identifying channels that have an “abnormal” level of noise • Threshold Scan: • Identifying dead channels, gain deteriorating effects, etc. • Delay Scan: • Identifying defects in the timing of the OT channels (offsets,non-linearities etc.) 1 TDC = 0.4ns; 1DAC = 0.1ns 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

19. Online-offline calibration software Noise level for the full detector <8*10-4 at working threshold • Noise Threshold Scan: • Identifying channels that have an “abnormal” level of noise • Threshold Scan: • Identifying dead channels, gain deteriorating effects, etc. • Delay Scan: • Identifying defects in the timing of the OT channels (offsets,non-linearities etc.) 99.7 % of the channels working in June 2011 1 TDC = 0.4ns; 1DAC = 0.1ns 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

20. Drift Time r 2.45 mm RT-relation • Majority of hits within 50ns readout window • RT-relation close to expectation from testbeam • Current single hit resolution (p>10GeV) of 220μm

21. Drift Cell Efficiency r 2.45 mm • Procedure: • Considered high quality track: • χ2 / dof < 2 • certain number of hits • Looking for hits along the track 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

22. Drift Cell Efficiency 99.2 - 99.5% average efficiency plateau r 2.45 mm • Procedure: • Considered high quality track: • χ2 / dof < 2 • certain number of hits • Looking for hits along the track • Characteristics: • Cell profile is symmetric • Efficiency inside the cell independent on the number of hits 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

23. Invariant-Mass Resolution Dimuon spectrum (3000-3800 MeV) • Momentum resolution p/p~0.35-0.5% • very good mass resolution • world best mass measurements Linear interpolation of invariant mass resolution Channel LHCb mass [MeV/c2] PDG [MeV/c2] 5279.17 ± 0.29 5279.50 ± 0.30 5279.50 ± 0.30 5366.30 ± 0.60 5620.2 ± 1.6 6277 ± 6 [LHCb-CONF-2011-027]

24. Upgrade Plans In 2010 run LHCb worked at 7 times its design conditions • run ~5 years (2011-2012 and 2014-2016), collect 5 to 6 fb-1 • upgrade ready for 2017-2018 shutdown, aim at >50 fb-1 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

25. Upgrade Plans In 2010 run LHCb worked at 7 times its design conditions • run ~5 years (2011-2012 and 2014-2016), collect 5 to 6 fb-1 • upgrade ready for 2017-2018 shutdown, aim at >50 fb-1 • Requirements: • Transmit collision data @ 40 MHz : • upgrade all FE to 40 MHz (new OTIS and GOL/AUX) • Re-use ASDBLR, HV board, FE mechanics (73% OT costs) 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

26. Upgrade Plans In 2010 run LHCb worked at 7 times its design conditions • run ~5 years (2011-2012 and 2014-2016), collect 5 to 6 fb-1 • upgrade ready for 2017-2018 shutdown, aim at >50 fb-1 • Requirements: • Transmit collision data @ 40 MHz : • upgrade all FE to 40 MHz (new OTIS and GOL/AUX) • Re-use ASDBLR, HV board, FE mechanics (73% OT costs) • Higher Luminosity = new IT/OT boundary • keep straw-tube technology or • possible partial replacement by 1mm SciFi in central region • Si -strips to be replaced • keep Si technology or • move to 250 m SciFi

27. Conclusions • OT: drift-chambers detector based on straw tube technology • Detector performance according to expectations • Continuous monitoring and replacement of FE Electronics guarantees efficient data taking • Excellent mass resolution • Ageing problems traced back to the plastifier in the sealing glue • Addition of oxygen to the gas mixture to reduce gain loss • HV training technique to remove the deposit on the wire • A lot of work ongoing to be ready for an upgrade 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo