ECAL Studies for the CLIC_ILD detector

1. ECAL Studies for the CLIC_ILD detector Jacopo Nardulli, CERN LCD

2. Why the ECAL is as it is ? • The LOI ILD Ecal structuring comes from an optimization from H. Videau available here ECAL Optimization from H. Videau • A few scenarios with different nr of layers and different absorber thickness are considered • Similar studies have also been done by M.S.Amjad and have been presented at the CALICE Meeting in Casablanca

3. Goal of this study • Attempt a similar optimization on the CLIC version of the ILD detector • To have an ECAL with less layers, therefore cheaper, but without degradation of the performance • From our vol 2 CDR, cost chapter • You see ECAL contribution (~30% ?)

4. Two possible studies • Fix the radiation length • But decrease the Nr of ECAL layers • Less expensive, energy resolution can be worse, as the pattern recognition • How to ? • Varying nr of layers and absorber thickness, • not the Si thickness • Vary the radiation length • And decrease the Nr of ECAL layers • Less expensive, overall performance changes • If I change the X0, can have more leakage into the HCAL • Varying nr of layers, absorber thickness and studying performance as a function of the X0

5. Now only first study: Different ECAL models • Altering the number of layers and their absorber thickness in such a way that Total Absorber thickness in the detector remains the same. • The analyses in this talk are done with PandoraPFA with • Single Photon with θ and φ varying in the full range and Energies of 1, 10, 100 and 500 GeV and using • With Z  uds events of 91, 200, 500 and 1000 GeV • Default model 20 layers in 1st stack and 9 layers in 2nd stack

6. Results for single photons

7. Results: changing Nr of layers in 1st stack Mean Rec. Energy vs Input Energy [%] Energy Res. vs Input Energy

8. Results: changing Nr of layers in 2nd stack [%] Energy Res. vs Input Energy

9. Results: changing Nr of layers in 1st and 2nd stack [%] Energy Res. vs Input Energy • Preliminary conclusion: • Can go from 29 layers to 25 with hardly any loss in performance

10. Results: just 1 stack [%] • Preliminary results • Using just 1 stack with less, but thicker, layers does not seem to degrade the energy resolution dramatically.

11. Results for Z  uds events

12. Results: changing Nr of layers in 1st stack

13. Results: changing Nr of layers in 2nd stack

14. Results: changing Nr of layers in 1st and 2nd stack Energy Res. vs Input Energy

15. Results: just 1 stack

16. Conclusions • First attempt of an optimization of the ECAL for CLIC_ILD • First results show that we can go from 29 to 25 layers with a small loss in performance • Using just 1 stack with less, but thicker, layers does not seem to degrade the energy resolution dramatically. • Results described in LCD-Open 2011-004 document, available here

17. Next steps • Preliminary studies, lots of things not considered • i.e. is it right to use PFA ? Or should we use Garlic ? • Is the energy resolution the main/only parameter to be used to understand possible loss of performance caused by having less layers ? • Finish 1st study • More statistics • Use RMS90 • Move to the 2nd study • Performance as a function of the X0

18. Backup

19. Results: changing nr layers in 2nd stack Mean Rec. Energy vs Input Energy

20. Only 1 layer

21. Results: changing Nr of layers in 1st and 2nd stack Mean Rec. Energy vs Input Energy

22. Disclaimer • Here showing the Energy Resolution vs. the Energy and using Single Gaussian fits • To get the energy resolution I am NOT using the official MarlinProcessor which calculates rms90 and mean90 • So do not look at absolute numbers, but at the general trend of the plots

23. Results: changing Nr of layers in 1st and 2nd stack and different ratios • Reducing the X0 in 1st stack and changing the ratio does not seem to help. • Now try something else

24. Thickness of layers