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.

MVD Tutorial, Tobias Haas, DESY

Today:



Motivation



Hardware



DAQ & R/O



DQM



Radiation monitoring



Alignment/Tracking



Summary

MVD Tutorial, Tobias Haas, DESY

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

 MVD Tutorial, Tobias Haas, DESY

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

MVD Tutorial, Tobias Haas, DESY

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

MVD Tutorial, Tobias Haas, DESY

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.

MVD Tutorial, Tobias Haas, DESY

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

MVD Tutorial, Tobias Haas, DESY

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.

MVD Tutorial, Tobias Haas, DESY

Stability < 20 μm

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!

MVD Tutorial, Tobias Haas, DESY

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