1. A. SarratTPC jamboree, Aachen, 14/03/07 1 Full Monte Carlo of a TPC equipped with Micromegas Antony Sarrat CEA Saclay, Dapnia Motivation Simulation content Comparison with data

2. A. SarratTPC jamboree, Aachen, 14/03/07 Introduction T2K near detector will have 3 TPCs used for momentum measurement and e/  separation. A TPC equipped with Micromegas detector was tested at CERN in Nov. 2005 Monte Carlo simulation of these tests

3. A. SarratTPC jamboree, Aachen, 14/03/07 Cosmic Setup Micromegas End-plate Ex-HARP TPC field cage ~ 154 cm ~ 1300 cm 2 instrumented ~1.5m drift length

4. A. SarratTPC jamboree, Aachen, 14/03/07 Simulation

5. A. SarratTPC jamboree, Aachen, 14/03/07 Simulation Content Primary generation Tracking Electrons creation and transport Amplification in Micromegas Electronics (ALTRO, Alice TPC Readout)

6. A. SarratTPC jamboree, Aachen, 14/03/07 Primary Generator Cosmic spectrum or 55 Fe source (5.9 keV  ) Primary Spectrum (GeV) PP This generator was not tuned to reproduce perfectly the setup. It roughly reproduces the characteristics of the trigger planes (above and below the TPC field cage) and the μ angular distribution and spectrum.

7. A. SarratTPC jamboree, Aachen, 14/03/07 Tracking GEANT 4 does the tracking and simulates the energy loss in the gas. Physics processes: low energy EM processes delta-rays production

8. A. SarratTPC jamboree, Aachen, 14/03/07 Ionization Number of electrons: N = E loss / W I with W I = 26 eV (Sauli) Step ≤ 1mm N elec ~ 100 cm -1 (mean) N elec ~ 60 cm -1 (peak) N elec

9. A. SarratTPC jamboree, Aachen, 14/03/07 Drift And Diffusion Magboltz calculation Drift speed V drift = 6.5 cm.  s -1 Diffusion coefficient  L = 290  m.cm -1/2  T = 240  m.cm -1/2 @ 0.2T with Gaussian distributions B = 0.2T

10. A. SarratTPC jamboree, Aachen, 14/03/07 10 Amplification Simulate gain distribution with an exponential distribution (Furry). Polya distribution was also investigated, but it is not needed to reproduce data. -----  =0.0 - - -  =0.5 Charge per row (ADC)

11. A. SarratTPC jamboree, Aachen, 14/03/07 Electronics 4 th order semi-gaussian filter (X e -X ) 4 with X = (T - T 0 ) /  and  = 190 ns ALTRO electronics (Alice TPC Readout) Charge (ADC) Time (100ns) Data - X 4 e -4X

12. A. SarratTPC jamboree, Aachen, 14/03/07 Data / MC Comparison

13. A. SarratTPC jamboree, Aachen, 14/03/07 Gain Tuning 55 Fe radioactive source dataSimulation of 55 Fe photons Larger  in data: the Fano factor is not introduced in the fluctuations Other possibles sources: - Transparency of the mesh ? - Channel to channel fluctuations ? Charge (ADC)

14. A. SarratTPC jamboree, Aachen, 14/03/07 14 Energy Loss Distribution of the charge per row for data/MC Calculating N elec from Geant E loss (N elec =E loss /W I ) Adding Landau fluctuations to the average number of electrons N elec Data MC Data MC Charge per row (ADC)

15. A. SarratTPC jamboree, Aachen, 14/03/07 15 Estimated Track Width Estimated track width vs drift distance for data/MC Data MC

16. A. SarratTPC jamboree, Aachen, 14/03/07 Fraction of Pad Per Cluster Cumulative fraction of pad per cluster vs drift distance for data/MC  Data  MC 1 pad 2 pads

17. A. SarratTPC jamboree, Aachen, 14/03/07 Resolution Residuals Gaussian width of two pads clusters vs drift distance for data/MC Data MC

18. A. SarratTPC jamboree, Aachen, 14/03/07 Conclusion A full Monte Carlo simulation of a TPC is written for T2K’s near detector, using Geant 4. Data and MC are in fair agreement Energy deposition needs to be better understood

19. A. SarratTPC jamboree, Aachen, 14/03/07 19 Energy Loss Resolution Energy loss resolution for data and MC. Data MC Charge (ADC) Energy loss calculated from 80% truncated mean of the distribution of the total charge in each row.  ~ 13% for both data and MC

20. A. SarratTPC jamboree, Aachen, 14/03/07 20 J.Derré Toy Monte-Carlo

21. A. SarratTPC jamboree, Aachen, 14/03/07 21 J.Derré

22. A. SarratTPC jamboree, Aachen, 14/03/07 22 J.Derré

23. A. SarratTPC jamboree, Aachen, 14/03/07 23 J.Derré

24. A. SarratTPC jamboree, Aachen, 14/03/07 24 J.Derré

25. A. SarratTPC jamboree, Aachen, 14/03/07 25 J.Derré

26. A. SarratTPC jamboree, Aachen, 14/03/07 26 J.Derré