Mitglied der Helmholtz-Gemeinschaft Calibration of the COSY-TOF STT & pp Elastic Analysis Sedigheh...
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Transcript of Mitglied der Helmholtz-Gemeinschaft Calibration of the COSY-TOF STT & pp Elastic Analysis Sedigheh...
![Page 1: Mitglied der Helmholtz-Gemeinschaft Calibration of the COSY-TOF STT & pp Elastic Analysis Sedigheh Jowzaee IKP Group Talk 11 July 2013.](https://reader037.fdocument.pub/reader037/viewer/2022102818/56649f465503460f94c67bc0/html5/thumbnails/1.jpg)
Mitg
lied
der H
elm
holtz-G
em
ein
schaft
Calibration of the COSY-TOF STT & pp Elastic Analysis
Sedigheh Jowzaee
IKP Group Talk11 July 2013
![Page 2: Mitglied der Helmholtz-Gemeinschaft Calibration of the COSY-TOF STT & pp Elastic Analysis Sedigheh Jowzaee IKP Group Talk 11 July 2013.](https://reader037.fdocument.pub/reader037/viewer/2022102818/56649f465503460f94c67bc0/html5/thumbnails/2.jpg)
Outline
• COSY-TOF Spectrometer
• STT calibration goal
• Calibration comparison
• pp elastic analysis of data 2012
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COSY-TOF Spectrometer
• Strangeness physics pp→ pK+ Λ pπ3
p
p
π-
K+
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COSY-TOF STT• Installed in vacuum tank
• Consists of 2704 straw 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
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Calibration Procedure
• Motivation for precise STT calibration• Reconstruction of events with STT at COSY-TOF • Event analysis based on the vertices reconstruction of the
charged final state particles (p, K, Λ p, π-)• Calibration steps
• TDC correction• Multiple hits removal• Signal width cut• Electronics offset correction
• Estimation of correlation between drift time and radius• Straw layers position correction
• pp elastic events measured in Fall 2012 at pbeam=2.95 GeV/c are analyzed for the calibration of the STT
• Data taking in November 2012 for 4 weeks
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TDC Correction
• First hit selection• Signal width cut
– 5ns width limit of readout electronics
Using the common-stop readout of the TDCs, higher values correspond to shorter drift times
raw TDC spectrum for 5.106 hits in the 3 double layers straw tubes
TDC spectrum after first hit selection and width cut
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Due to the positioning of tubes in dls (Time of flight)
TDC Correction
• Electronics offset correction• Different readout modules• Correction with fit method
• Ref. point=turning point of error function + 1σ
• Offset= 780 ns(arbitrary)-Ref. point
Turning point
σ
7
Due to the positioning of readout board
Due to applying 3 racks of readout electronics
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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)
Track
Straw Tube
Isochrone radius: cylinder of closest approach of the particle track to the wire
8
Risochrone
min)()()( RN
NRRdttvtr
tot
iwiretubedrifti
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Auto-Calibration Method• Track reconstruction with averaged r(t) curve of 3 groups of double layers
from self-calibrating method was done• Track parameters were analyzed to find the most probable correlation
between drift time and isochrone radius (track to wire distance)
distance to wire vs. drift time shift vs. isochrone radius
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STT Resolution• Residual=|d| – r d: track to wire distance, r: isochrone radius
• Spatial resolution: width of the Gaussian fit functions to the residual distribution as a function of drift time or radius
• The resolution at 0.25 cm averaged over all double layers is 142 ± 8 µm
residual vs. drift time resolution vs. isochron radius
Residual vs. isochron radius10
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Residual Comparison
New calib.
Old calib.
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dl 5 dl 13
dl 5 dl 13
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Resolution Comparison
New calibration
Old calibration
Resolution at 0.25 cm New: 142±8 µmOld : 174±18 µm
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pp Elastic Analysis
beampppyCoplanarit ˆ)ˆˆ( 21 )()( 21arg EEEEE ettbeammiss
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pbeam ptarget
p1
p2
θ1
θ2
φGeometry of pp elastic events
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pp Elastic Analysis
1)20
()5
( 22
MeV
E
mrad
C
selectioncircular
miss
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After coplanarity cut
After circular cut
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Vertex Distribution
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• Dependent on the beam properties
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Vertex Distribution• Dependent on the target dimension
target dimension=5.17±0.03 mm
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Closest Approach of Tracks
• Minimum distance of the two proton tracks of selected pp elastic scattering events
• Independent on the beam properties
• Dependent on the STT reconstruction precision
• Improvement of FWHM 7.6%
FWHM=1780 µm new calibration
FWHM=1920 µm old calibration
• Improvement in reconstruction accuracy
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Summary
• Signal width cut is effective to remove noise
• Electronics offset correction reduced the systematic error from different electronics modules and time of flight
• Improved spatial resolution 142 ±8 µm at 0.25 cm averaged over all double layers compared to the old calibration with same beam momentum (174 ±18 µm)
• The new calibration improved track reconstruction accuracy for pp elastic scattering events
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Mitg
lied
der H
elm
holtz-G
em
ein
schaft
Thank you
![Page 20: Mitglied der Helmholtz-Gemeinschaft Calibration of the COSY-TOF STT & pp Elastic Analysis Sedigheh Jowzaee IKP Group Talk 11 July 2013.](https://reader037.fdocument.pub/reader037/viewer/2022102818/56649f465503460f94c67bc0/html5/thumbnails/20.jpg)
Mitg
lied
der H
elm
holtz-G
em
ein
schaft
Backup slides
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Straw hits
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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
![Page 23: Mitglied der Helmholtz-Gemeinschaft Calibration of the COSY-TOF STT & pp Elastic Analysis Sedigheh Jowzaee IKP Group Talk 11 July 2013.](https://reader037.fdocument.pub/reader037/viewer/2022102818/56649f465503460f94c67bc0/html5/thumbnails/23.jpg)
Monte Carlo Comparison
New calibration -2012
calibration-MC-2012
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Beam Direction
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Beam Polarization
• distribution of asymmetry is fitted with the ā(θ*)cos(φ)
• The analyzing power A(θ*) is taken from the partial wave analysis Said
• calculated beam polarization
(69.9±10.0)%
Azimuthal asymmetry of elastic scattering events in
pppp
]60,45[
)()cos(
),()(
),(
)cos(
),(
)(
1
**
*
*
*
*
aconsta
AP
NN
NNa
a
AP
beam
beam
25