1. Reconstructing energy from HERD beam test data Zheng QUAN IHEP 3 rd HERD work shop Xi’an, 20 Jan.2016 0

2. What does ICCD raw data look like Images of 250 WLS fibers on 300×400 pixels CCDs Each pixel has a digitized gray value proportional to the light intensity 1

3. Crystal/WLSF array coordinate One frame of 40GeV electron run C2X crystals: center of crystal array, directly hit by beam particles, most probably deposited high energy ; Higher deposited energy means larger spot, needs more space to weaken or avoid overlapping. 2

4. 3 Fitting or merging a. Fitting the shape of 1MIP spot with gaussian function: sigma~1.3 pixels, maybe the bin size is not small enough to make a precise fitting

5. 4 b. Change of shape: high energy deposited, over saturated; c. Unsymmetrical shape.

6. Energy reconstruction step 1: Summing gray values(merging pixels) Merging area: approximated circle, radius = 5 pixels, center = COG(gray value weighted) Light intensity distribution on CCD doesn’t change with Light intensity; 5

7. Fitting: Lan×Gaus(left peak) + Lan×Gaus(right peak), MIP = MPV(right) – MPV(left) Energy reconstruction step 2: Calibrating low range ICCD using pion beam Event Selection: ~40% incident particles do not initiate showers 6 1MIP ≈ 0.03GeV

8. Energy reconstruction step 3: Fitting baseline Low range ICCD High range ICCD The pixels on high range ICCD have a larger fluctuation of response, indicating a wider baseline distribution 7

9. The MPV of baseline peak always deviates from 0 after baseline calibration. Fortunately, We can observe the baseline peak in every run. Low range baseline of A02 High range baseline of C24 8 Baseline

10. Energy reconstruction step 4: Image overlap(crosstalk) correction 9

11. Construct a Correction Matrix 10 Relative Crosstalk Value doesn’t change with light intensity. Very rough estimate Beam GeV

12. Energy reconstruction step 5: Calibrating high range ICCD Calibration factors: Great difference among CALO units… Expected factor: 0.025~0.033 11

13. Event Selection 1: Time dependent Good events: Before PS trigger, in a period of 3.3ms, no self trigger event comes 12

14. 13

15. Event Selection 2: Shower shape 14

16. 100GeV electron beam: contains 13% hadrons, 90% of hadronic events are excluded after selecting. Problem: What’s in this peak? 15

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18. Electron energy Slope<1, due to energy deposition in carbon structure and energy leakage. 17

19. Energy resolution Electron 18

20. Angle reconstruction 19

21. 20 Gap = 5mmGap = 2mm

22. Proton Event Selection: Enough valid hits to exclude MIP events; Shower maximum is contained; Shower starts at first few layers; 21

23. 22

24. Problems and discussions: Longitudinal Shower Shape 23 Electron 100GeV

25. 24 For layer 2, layer 3: Energy deposited in central units are higher than expected(C21,C22); For layer 4, layer 5: Energy deposited in CALO units around the central units are lower than expected.

26. 25 C20C21C22

27. 26 Problems and discussions: Strange excess on the right of main peak Main peak Right peak

28. 27 Self trigger system: no peak on the right Self Trigger system VS reconstructed energy from ICCD Right peak Right peak disappears after excluding E>120GeV events So the right peak is probably from ICCD

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30. Problems and discussions: charge detection C20: the first layer of central CALO Units 29 Quenching?

31. 30 Problems and discussions: About energy resolution… Slightly saturated

32. 31 With high rangeWithout high range

33. Summary 32