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Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK 1
Charles UniversityPrague
Zdeněk Doležal for the DEPFET beam test group
3rd Open Meeting of the Belle II Collaboration
DEPFET Beam Test 2008 Results
Charles University in Prague
Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK 2
Charles UniversityPrague
Beam test 2008 tested ILC type of DEPFET detectors
Test particles: pions 120 GeV
Thickness of sensors: 450m (Belle II: 50 m)
Complication with multiple scattering
Pixel size ~ 24 – 32 m (Belle II: ~ 60 – 90 m)
Expected resolution < 2 m (Belle II: ~ 8 m)
Self-telescoping system
Special methods for data analysis (for separation of detector precision from other effects)
Belle II type of DEPFET detector expected for beam testing in 2010
Introduction
Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK 3
Charles UniversityPrague
Special scans performed:
Edge scan (to study edge effects)
Energy scan
Angle scan
Bias voltage scan
High statistics scan for stability checking
Introduction (2)
Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK 4
Charles UniversityPrague
SC 0: 2 5x25x4mmSC 1: 4 x4 x4m m
-12 5 0 79 21 3 40 8 55 1 63 1 72 2Po sit ion
[m m] :0 1 2 3 4 5Po sit ion :
Bea m
D epfe t2: M E, C C G, PXD 5, S9 0K02 , 0.0 32x0.0 24m m
D epfe t6: M E, C C G, PXD 5,S9 0I03 , 0.0 24x0.0 24m m
D epfe t14: ME, CC G, PXD 5, 9 0K02 , 0.0 32x0.0 24m m
D epfe t7: M E, C C G, PXD 5, 9 0I00 , 0.0 32x0.0 24m m
D epfe t5: M E, C C G, PXD 5, 1 4B, S9 0I00 , 0.0 32x0.0 24m m
D epfe t11: ME, SIMC , PXD 5, S9 0K00 , 0.0 32x0.0 24m m
Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK 5
Charles UniversityPrague
Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK 6
Charles UniversityPrague
The ‘underwear’: Power supplies
Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK 7
Charles UniversityPrague
Pre-tracking steps: Common-mode noise correction Gain correction COG production (position error estimations) Alignment and corrections in several steps
Full resolution analysis with residuals, resolution analysis, track precision estimation, telescope resolutions etc.
Verification of analysis with simulated data GEANT4 simulation (TB2008 geometry,
experimental detector resolutions simulated by Gaussian smear, analyzed in a standard way)
Description of analysis
Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK 9
Charles UniversityPrague
Analysis results
Seed chargeTotal (cluster) charge Cluster size
Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK 10
Charles UniversityPrague
Residuals (plots are in log scale): non-Gaussian tails at a 1 percent level
Residuals
Module 0 Module 1 Module 3Module 2 Module 5Module 4
Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK 11
Charles UniversityPrague
Verification of analysis with simulation data
Resolutions reproduced from analysis of simulated data with realistic detector resolutions included
Agreement in resolutions of all detectors within ±5% (±0,1 µm)
Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK 12
Charles UniversityPrague
Typical results of DEPFET sub-pixel analysis: map of resolutions in pixel area. Color scale runs between 1 - 4 m. First row shows modules #0, x and y axis , #1 x and y axis, second row shows modules #2 x and y axis , #3 x and y axis, third row shows modules #4 x and y axis and #5 x and y axis.
Sub-pixel analysis results
Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK 13
Charles UniversityPrague
Changing bias affects seed and cluster size Does not affect cluster charge and resolution
Conclusion from bias scan
RMS residuals vs. bias, module 3 (pixel size: 24 x 24 m)
1
1.2
1.4
1.6
1.8
2
2.2
2.4
150 170 190 210 230
Bias [V]
Re
sid
ua
ls [
m]
Resid Mod 3 xResid Mod 3 y
Cluster charge and seed vs. bias, module 3 (pixel size: 24 x 24 m)
0
200
400
600
800
1000
1200
1400
1600
1800
150 170 190 210 230Bias [V]
Va
lue
[A
DU
]
Cluster_Charge_3 Seed_3
Cluster size vs. bias, module 3 (pixel size: 24 x 24 m)
0
1
2
3
4
5
6
7
150 160 170 180 190 200 210 220 230
Bias [V]
Clu
ste
r s
ize
Seed
Cluster charge
Cluster size
Residuals
Resolutions
Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK 14
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Relative deviations of resolutions, comparison of data and simulations. Solid circles are simulations, open circles are data; green - "diagonal" estimates, red - ML estimates. Simulation data are relative deviations of resolutions (green - "diagonal“ estimate, red - ML estimate) with energy, as seen in analysis of GEANT4 simulation data. For reference, we also plot residuals (blue). The data for each energy are based on analysis of 100 replicas of a data file containing 10,000 tracks.
The plotted values are (xE - xtrue)=xtrue for simulations, and (xE - x120GeV )=x120GeV for data.
The reasons of discrepancy are under study.
Conclusion from energy scan
Beam test results
Beam test and simulation
Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK 15
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Expected behaviour: rising cluster charge between 0 and ±4 deg (longer path) effects of larger cluster size above ±4 deg
here 2x2 pixels summed only
Cluster charge and seed in the angle scan
Cluster charge and seed vs. angle, module 3 (pixel size: 24 x 24 m)
0
200
400
600
800
1000
1200
1400
1600
1800
-8 -6 -4 -2 0 2 4 6
Angle [deg]
Va
lue
[A
DU
]
Seed_3 Cluster_Charge_3
Cluster size vs. angle, module 3 (pixel size: 24 x 24 m)
4.4
4.5
4.6
4.7
4.8
4.9
5
5.1
5.2
5.3
5.4
-8 -6 -4 -2 0 2 4 6
Angle [deg]
Clu
ste
r s
ize
Linear increase of cluster size above ±1 deg.
Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK 16
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Best resolution within ±1 deg (agreement with simulations)
Resolution in the angle scan
Residuals and resolution vs. angle, module 3 (pixel size: 24 x 24 m)
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
-8 -6 -4 -2 0 2 4 6
Angle [deg]
Va
lue
[
m]
Resid Mod 3 x Resid Mod 3 y
Resol Mod 3 x Resol Mod 3 y
Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK 17
Charles UniversityPrague Point Resolution in Z
In many cases at normal incidence only one row is fired : resolution is limited by pixel size
When track is inclined more than onerow is fired -> resolution gets better
At shallow angles cluster size gets extremely large and simple centre-of-gravity approach yields poor resolution due to inter-pixel charge fluctuations. Resolution is improved by means of η-algorithm (edge-technique)
Point Resolution in Z
A. Frey, MPI München 3/08/2006 DEPFET Workshop Bonn
Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK 19
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Analysis of DEPFET TB2008 is almost complete
Presented final results for: individual detector resolutions resolution vs. interpixel position influence of edge voltage energy scan resolution vs. bias resolution vs. incidence angle
Summary of obtained resolutions:
To do: high statistics scan analysis
Conclusions
Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK 20
Charles UniversityPrague
The analysis shows • Consistent behaviour of tested DEPFET modules over the whole course of the beam test. • Response to 120 GeV pions (110 keV deposited energy) was over 1600 ADU at ~13 ADU noise for the DUTs, which gives S/N over 120.
• For modules thinned to 50 m (prepared for Belle II) the S/N of 13 can be expected. An increase of 10 % can be gained with newly developed electronics (DEPFET sensor contributes to the measured noise by 10 % only, the rest comes from the current electronics). • The effects of different cluster size have to be tested. The expected resolutions for thinned sensor below 2 m are very promising. • Detailed resolution scans show ~0.3 m variation of resolution over the pixel area• Detailed results available in a DEPFET Note
Conclusions