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

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

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

OT: the detector oDrift Chambers detector based on straw tube technology: oAnode wire at 1550 V oCathode straw connected to ground oGas Mixture Ar/CO 2 /O 2 (70/28.5/1.5) Straw tubes packed in double- layered modules Type F 2400 mm S mm S3 S mm 4 3 stations for each side Each station 4 layers (central layers tilted by ± 5°)

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

Quality assurance 6 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) Quality Assurance during production: oWire tension oDark current oWire pitch Quality Assurance after production: oGas Tightness, Dark current odetector response to 90 Sr β- source Full scan (every cm 2 ) of all OT modules Excellent uniformity of the response for all modules 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference, Como Villa Olmo

Nasty Surprise: Ageing 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 Ratio Plot: I after /I before Irradiated with a 2 mCi 90 Sr source Octorber 2011 Barbara Storaci 13th ICATPP Conference, Como Villa Olmo

Nasty Surprise: Ageing 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 Ratio Plot: I after /I before Irradiated with a 2 mCi 90 Sr source CULPRIT C 16 H 22 O 4 C 16 H 20 dibutyl phthalate diisopropyl-naphthalene AY103 AY103-1 Supplier produced the glue with a different plastifier: same mechanical properties… but AY103-1 causes ageing!!! Octorber 2011 Barbara Storaci 13th ICATPP Conference, Como Villa Olmo

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

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 10 Wire with carbon deposit 3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference, Como Villa Olmo

Recovery and Prevention: HV training Before training (previous damages clearly visible) After 15h training at 1900V in situ (only wires 33-64) 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 recovery immunity Octorber 2011 Barbara Storaci 13th ICATPP Conference, Como Villa Olmo

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) events per step 12 No gain loss beyond 10% observed yet

Readout Monitoring 13

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

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

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

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

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

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

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

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

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

Invariant-Mass Resolution  Momentum resolution  p/p~ %  very good mass resolution  world best mass measurements [LHCb-CONF ] Channel LHCb mass [MeV/c 2 ] PDG [MeV/c 2 ] ± ± ± ± ± 6 Dimuon spectrum ( MeV) Linear interpolation of invariant mass resolution 23

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

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

Upgrade Plans In 2010 run LHCb worked at 7 times its design conditions Requirements: 1.Transmit collision 40 MHz : upgrade all FE to 40 MHz (new OTIS and GOL/AUX) Re-use ASDBLR, HV board, FE mechanics (73% OT costs) 2.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 run ~5 years ( and ), collect 5 to 6 fb -1 upgrade ready for shutdown, aim at >50 fb -1 26

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 Octorber 2011 Barbara Storaci 13th ICATPP Conference, Como Villa Olmo