Calibration of a Modular Straw-Tube- Tracker for the COSY-TOF Experiment Sedigheh Jowzaee 3-6 June 2013, Symposium on Applied Nuclear Physics and Innovative Technologies, Krakow, Poland INTERNATIONAL PHD PROJECTS IN APPLIED NUCLEAR PHYSICS AND INNOVATIVE TECHNOLOGIES This project is supported by the Foundation for Polish Science – MPD program, co-financed by the European Union within the European Regional Development Fund

Outline COSY facility & COSY-TOF Spectrometer COSY-TOF Straw-Tube-Tracker (STT) STT calibration goal Calibration approach Apply Corrections Find R-T correlation 2

COSY facility COSY: Cooler Synchrotron Polarized and unpolarized beams of protons and deuterons Momentum range 600 MeV/c to 3.3 GeV/c medium energy physics program Cooler & storage ring circumference 184 m High precision beam by: electron and stochastic cooling 4 internal experiment ANKE, PAX, WASA, EDDA 2 external experiment TOF, PANDA test 3

COSY-TOF Spectrometer Strangeness physics 3 m 4

COSY-TOF STT Installed in vacuum tank Consists of 2704straw tubes with Ø=10 mm & 1050 mm length Organized in 13 double-layers Filled with Ar/CO2 gas at 1.2 bar overpressure Fixed in 3 orientations with angle 60˚ to each other for 3D track reconstruction 5

STT readout electronics 6 Amplifier-shaper- discriminator chip ASD-8 Preamplifier Time measurement ASD-8 input board: Impedance matching and shaping for ASD-8 chip ASD-8 chip: Short measurement time (10 ns) Good resolution (25 ns) Low operational threshold (2 fC) Shaper with pole-zero cancelation In the vacuum tankOut of the vacuum tank

STT information Information from straws Beam hole leading edgetrailing edge 7

Calibration motivation Reconstruction of events with STT at COSY-TOF Precise reconstruction of vertices Reducing background for better resolution Event analysis based on the vertices reconstruction of the charged final state particles (p, K, Λ p, π) Precise calibration needed Different effects should be considered Multiple hits removal Signal width cut Electronics offset correction Straw layers position correction pp elastic events measured in Fall 2012 at p beam =2.95 GeV/c are analyzed for the calibration of the STT 8

Calibration Multiple hits removal Track Straw Tube Wire e raw TDC spectrum for hits in the 2704 single straw tubes TDC spectrum after removing multiple hits Using the common-stop readout of the TDCs, higher values correspond to shorter drift times 9

Calibration Signal width cut Some noisy hits remain after removing multiple hits STT electronics readout has a 5ns signal width limit between leading and following trailing edge Only noise can produce width lower than 5ns Record leading edge time without trailing edge time The width spectrum was cut for less than 5ns 10

Calibration Signal width cut effect TDC spectrum before the signal width cut TDC spectrum after a cut on the signal width 11

Calibration Electronics offset correction Different readout modules Correction with fit method Error function was fitted to the leading edge of TDC spectrum for each straw χ2/NDF 2 Ref. point=turning point of error function + 1σ Offset= 780 ns(arbitrary)-Ref. point Turning point σ 12 complementary error function

Calibration Electronics offset correction Fit-functions were defined for empty or improper fitted straw tdc spectra 13

Calibration Electronics offset correction effect 14

Drift time Corrected drift time spectra Maximum drift time 145 ns Same drift time spectrum within each double layer Irregular shape and tail part in first 4double layers Improper recognition of first hits due to low sensitivity of their electronics Events mixing and tail pile-up 15

Self-calibrating method Main aim: determination of the correlation between the drift time and the isochrone radius Isochrone radius was calculated for each bins of drift time ( homogeneous illumination assumption in whole straw) N i : no of tracks in t 0 to t i Track Straw Tube R isochrone R tube 16 Isochrone radius: cylinder of closest approach of the particle track to the wire

TDC time vs isochrone radius for double layer-13 Distance to track calibration method Track reconstruction with averaged R-T curve from self-calibrating method Track parameters were analyzed to find the most probable correlation between TDC time and isochrone radius (track to wire distance) TDC time vs distance to wire for double layer-13 17

STT resolution In Ideal case the R-T curve should be same for all straws The averaged R-T curve from 3 groups of double layers was used for all straws Residual=|d| – r d: track to wire distance, r: isochrone radius Spatial resolution: width of the gaussian+pol4 fit functions to the residual distribution as a function of TDC time Average resolution at 0.25 cm over all double layers is 142 ± 8 µm TDC time vs residual for double layer Resolution vs isochron radius for double layer-13

Summary Signal width cut is effective to clean noisy channels Electronics offset correction was applied well to reduce the systematic error from different electronics modules For the first time the same Self calibrating R-T curve was used for track reconstruction within each double layer Improved Average spatial resolution 142 ±8 µm at 0.25 cm over all double layers was found compare to the last calibration with same beam momentum (170 ±11 µm) by taking an average R-T curve The new calibration improvement is studying with comparison of pp elastic parameters (i.e. vertex resolution) to the former work. 19

Thank You 3-6 June 2013, Symposium on Applied Nuclear Physics and Innovative Technologies, Krakow, Poland INTERNATIONAL PHD PROJECTS IN APPLIED NUCLEAR PHYSICS AND INNOVATIVE TECHNOLOGIES This project is supported by the Foundation for Polish Science – MPD program, co-financed by the European Union within the European Regional Development Fund

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STT inefficiency STT is the base detector for track reconstruction Low detection efficiency or not response Mechanical problem or electronics Electronics problemMechanical damage noise hits

2 electron clusters

error function complementary error function