Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK1 Charles University Prague 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, KEK2 Charles University Prague  Beam test 2008 tested ILC type of DEPFET detectors  Test particles: pions 120 GeV  Thickness of sensors: 450  m (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, KEK3 Charles University Prague 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, KEK4 Charles University Prague

Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK5 Charles University Prague

Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK6 Charles University Prague The ‘underwear’: Power supplies

Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK7 Charles University Prague 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, KEK8 Charles University Prague Some LSR effects over detector area was identify and correct Large scale response (LSR) correction Y axis: ±20  m Confirmation of effect using laser testing – sharing of this up to 100  m Study of this effect is continuing. For Belle II concept this effect is negligible Changing edge voltage does not influence the edge effect in LSR

Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK9 Charles University Prague Analysis results Seed chargeTotal (cluster) chargeCluster size

Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK10 Charles University Prague Residuals (plots are in log scale): non-Gaussian tails at a 1 percent level Residuals Module 0Module 1Module 3Module 2Module 5Module 4

Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK11 Charles University Prague 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, KEK12 Charles University Prague Typical results of DEPFET sub-pixel analysis: map of resolutions in pixel area. Color scale runs between  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, KEK13 Charles University Prague  Changing bias affects seed and cluster size  Does not affect cluster charge and resolution Conclusion from bias scan Seed Cluster charge Cluster size Residuals Resolutions

Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK14 Charles University Prague 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 (x E - x true )=x true for simulations, and (x E - x 120GeV )=x 120GeV 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, KEK15 Charles University Prague 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 Linear increase of cluster size above ±1 deg.

Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK16 Charles University Prague Best resolution within ±1 deg (agreement with simulations) Resolution in the angle scan

Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK17 Charles University Prague 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 one row 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, KEK18 Charles University Prague 1.Gain correction should be done during characterization for every pixel 2.Why is there LSR effects? “V” and “Edge” effects? (design issue?) Laser test confirm existence of this effect. 3.Mechanical movement of modules was observed in level of 10 hours (~few tens of microns) – need to fix mechanical arrangement 4.Lack of good telescopes for routine testing of DUT. Systematic effects coming from non-diagonal elements of correlation matrix between detectors have influence to alignment, fitting of tracks and residual plot shape. Simulation of geometry and all effects is needed for confirmation of results and elimination of systematic effects. Comments and open questions (important messages to R&D community)

Jyly 8, 2009, 3rd open meeting of Belle II collaboration, KEK19 Charles University Prague 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, KEK20 Charles University Prague 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