Transcript The ZEUS Microvertex Detector
The ZEUS Microvertex Detector
Tobias Haas Deutsches Elektronensynchrotron ZEUS MVD Group: Bonn Univ., DESY-Hamburg, DESY-Zeuthen, Hamburg Univ., KEK-Japan, NIKHEF, Oxford Univ., Padova, Torino, Bologna, Firenze Univ. and INFN, UCL.
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Today:
Motivation
Hardware
DAQ & R/O
DQM
Radiation monitoring
Alignment/Tracking
Summary
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Requirements, Constraints, History
• Constraints: * Fit into existing ZEUS detector, * * * < Central tracker inner diameter ( ~32 cm) > elliptical beampipe (max. ~12 cm) Bunch crossing time 96 ns Operation at room temperature Extended interaction region in z direction • Requirements: * < 100 μm impact parameter resolution: < 20 μm intrinsic point resolution, 3 spatial measurements in two projections for each track, High (>97%) track efficiency.
• History: * * * * 1997: Approval 1997 – 2000: Construction 2000: First Cosmics 2001: Installation is ZEUS MVD Tutorial, Tobias Haas, DESY
Physics
Beauty
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MVD in Numbers
3(2) Barrel layers, 4 forward planes 38 mm <
R
< 247 mm -300 mm <
Z
7.6
0 < 750 mm <
θ <
160 0 Radiation < 300 kRad 207360 channels >99% single hit efficiency Currently: ca 12k dead channels (5.7%) 50 – 60 μm single hit resolution (goal: 20 – 30 μm) 130 – 150 μm vertex resolution (goal: < 100 μm) MVD Tutorial, Tobias Haas, DESY
Overview of the ZEUS MVD All cables in a Faraday cage The forward section: • 4 wheels • each one composed by 2 layers of 14 Si detectors • Total of 112 hybrids, >50k channels The barrel section: • 30 ladders • each one composed of 5 modules of 4 Si detectors • Total of 300 hybrids, >150k channels The read section: • Cooling pipes and manifolds • Distribution of FE, slow control and alignment cables MVD Tutorial, Tobias Haas, DESY
• • Single sided n-doped silicon sensors, 300 μm thick, p + strip implants, • Every 6 th read out (120 μm R/O pitch),
R Φ
and
Z
sensors are ganged, • Two planes are glued together to form a module with x-y readout.
• Helix3.0 analog R/O chip (Heidelberg/NIKHEF)
Barrel
• Five modules are mounted on a carbon fiber support structure to form a ladder. • The Si planes, Hybrids and Cabling are located on the 3 planes of the ladder • 30 ladders, in 3 planes, are positioned around the elliptical beam pipe in the MVD barrel detector MVD Tutorial, Tobias Haas, DESY
• The forward wheels have differently shaped detectors (trapezoidal with two different sizes to accommodate the beam pipe), • Two layers of single sided detectors, same pitch and construction as in the barrel, • strips cross at an angle of 26°.
Forward Wheels
• Same electronics and connectivity as in the barrel MVD Tutorial, Tobias Haas, DESY
Sensor/RO/Module
Sensor (Design) Helix (RO) Half Module
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per barrel layer
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Patch Box
to detector
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Other Components
Racks close to Veto wall area Cooling/SC HV/LV ADCs
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Signals
digitized signal analog signal S/N ~12-15
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dE/dx
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Detector Status (Pedestal run)
Barrel MVD
• Disabled Chips C1L05M0 Hlx 4-7 C1L07M0 All C1L07M4 Hlx 4-7 C2L00M3 Hlx 5 C2L01M0 Hlx 4-7 C2L02M4 All C2L05M0 Hlx 4-7 C2L09M4 Hlx 4-7 C2L15M4 Hlx 4-7 • Masked in DAQ since last Mar. C1L00M2 All C1L02M2 All C2L09M2 Hlx 4 W3S11 All
Forward MVD
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Detector Monitoring and Status:
• • • Dedicated runs (taken daily or when machine schedule allows): • Pedestals (noise) • Test pulse runs (gain and timing) • IV curves (bulk damage) • Laser alignment (mechanical stability) Online DQM: • Parasitic monitoring: • occupancies,
All Results
• cluster charges and widths • Immediate feedback for shiftcrew (hip)
DQM DB
Offline DQM: • Dedicated analysis of archived data before reconstruction: • Occupancies, • Cluster charges and widths • Hit maps • Bad/Noisy channel maps for reconstruction ( → gaf) MVD Tutorial, Tobias Haas, DESY
Radiation Monitoring
4 RadFET 4x2 PIN diodes FMVD zx-Querschnitt BMVD 4x2 PIN diodes 8 RadFET 8 RadFET 4 RadFET Z X z=160 cm 110 cm -60 cm -100 cm -120 cm -130 cm
PIN diodes:
Instantaneous dose from signal current (photo effect) → beam dump
RadFETs:
Integrated dose (Rad damage in FET → shift in threshold voltage)
-1.1m
-0.6m
-1.3m
-1.7m
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Radiation Effects
Signal:
↓
Noise: ↑
Sensor leakage currents: ↑
August 2002
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August 2002
rear forward forward
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bad
Bad Channels
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?
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MVD Reconstruction Suite
MVRECON (table: MVRECC) Standalone MVD reconstruction Calibrations, Dead Channel Treatment Clustering VCRECON, Pass 1 (table: ZTPRHL) Pattern Recognition First Track Fit KFRECON (table ZTTRHL, ZTTRPRM) Kalman Filter + Track Fit VCRECON, Pass 2 Primary and Secondary Vertexing Iteration is possible… … but not really foreseen … MVD Tutorial, Tobias Haas, DESY
MVRECON
Cluster
Cluster Threshold Strip Threshold Strips • Clustering a la “Online” • Cluster + Strip Threshold • Allow one strip below threshold • Add on the two side strips below threshold • Position Reconstruction MVD Tutorial, Tobias Haas, DESY
Efficiencies
Simulation All CTD tracks > 4 MVD hits > 2 MVD hits Φ Data Φ Note: Acceptance holes
Efficiency estimates from NC DIS: (Tracks in CTD and MVD fiducial) Data MC > 4 MVD hits 91.4% 93.8% > 2 MVD hits 99.3% 99.3% MVD Tutorial, Tobias Haas, DESY
Propaganda Events
Q 2
1200 GeV 2 Charged Current
Q 2
4500 GeV 2 Charged Current
Q 2
2800 GeV 2 Neutral Current
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Alignment
• 3 Step process: Survey of ladder positions before installation in the lab, Final alignment using cosmic data, Monitoring of stability using an in situ laser system with semi-transparent position sensors.
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Current Alignment
Track Residuals Impact Parameter
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Alignment … comments
Barrel Wheels
Only 1 (!) alignment exists Barrel could be better… … but the wheels have not even been touched.
Still dependent on standalone cosmic runs cosmics taken during beam are being studied … MVD Tutorial, Tobias Haas, DESY
Questions to the alignment
alignment procedure
position reconstruction in mvrecon
Effects of magnetic field
long term stability
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Peformance Estimate (R. Mankel)
D* tagged events allow to investigate the distance-of-closest approach (DCA) of the helices of K – and + DCA resolution-per-track ( DCA /√2) is a measure related to the impact parameter resolution independent of vertexing averaged over longitudinal (Z) and transverse (D H ) resolutions Compare to H1 published impact parameter resolution IP =33 m (90 m /p T ) At MC level our resolutions look reasonable Data: alignment key issue ZEUS data (2004 e+) ZTT H1 IP resolution (1/p T 1.4/p)
Alignment Monitoring: Laser Alignment
Typical Example of Measurement
• 5 laser beams (780nm, 5 mW), 7 sensors/beam, • Sensor gives position to • Data taken once per fill,
10 μm,
• Monitor deformations and define period of stability.
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Stability < 20 μm
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!
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Summary
• ZEUS MVD has completed the commissioning phase, i. e. design goals have been reached: • Reliable and well monitored detector operation (Data quality, radiation, alignment), • High tracking efficiency (>99%), • Precision needs to reach the goal (Impact parameter resolution
< 100 μm
).
• Dead channel development is worrying • Irradiation is under control but a constant concern.
• Alignment work needs to progress MVD Tutorial, Tobias Haas, DESY