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

Charles UniversityPrague

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

Charles UniversityPrague

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

Charles UniversityPrague

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

Charles UniversityPrague

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