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12/04/02  01/22/03  ….

“ miniTPC ” plus Double GEM Detector response simulation. Hit reconstruction precision. 12/04/02  01/22/03  …. R&D PHENIX “Wednesday’s meeting” ( status report ) N.Smirnov. Simulation approach (steps).

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12/04/02  01/22/03  ….

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  1. “miniTPC” plus Double GEM Detector response simulation. Hit reconstruction precision. 12/04/02  01/22/03  …. R&D PHENIX “Wednesday’s meeting” ( status report ) N.Smirnov

  2. Simulation approach (steps) • Number of ionization interactions / track in a gas ( F(βɣ)), and position in a space, or “photon absorption position” with “the width of ionization”. • Number of e- / interaction • Rectangle and chevron(s) shape of the pad • “history” of each e-: diffusion – hole – gas amplification – diffusion - hole – gas amplification –diffusion – pad row – pad FEE response ( t-shaping, noise)

  3. Simulation conditions • Particle (track) propagation in a gas – GEANT • Track position: more-less uniform distribution in drift direction; ~+/-16. deg slope both in xy and zy, picked to zero values. • Diffusion and Drift velocity is a Function (Gas, E, B). ( B=0.) • “Some model” - to calculate/simulate a GEM transparency. • Gas amplification – Polya distribution, and a function of “r-position” inside of the GEM hole • “Arriving” time on the pad for each e- + FEE t-shaping • Noise, “(F)ADC” response, pedestal, threshold to select “active” pads.

  4. Most probable pulse height from three anode strips (0.04 cm); measurement and simulation Double GEM Detector from CERN; 10x10 cm², 0.04 cm strips. – measurements were done with X-ray tube; 5.4 keV, 0.01 cm collimator, Ar+CO2(20%) B.Yu at al, IEEE, Nov ,2002 – Simulation

  5. Experimental data for TPC with double GEMs readout (small prototypes) are available (CERN, Canada, Munich, ….)

  6. “Canada Variant” FEE time response simulation FADC response for fixed pad row and “active” pads ( no noise). ADC channel t_bins, 5ns/bin

  7. Hit position reconstruction If number of active pads (in pad row) > 1. -- x_w = ∑(qi x x_pad) / ∑qi -- If number of active pads < 5 : gauss fit of a histogram (q – n of pad) was done with “special approach” for 2 active pads variant: ( “x_gf” ). Then line fit was done and hit residuals were calculated ---- all hits are in a fit: (“dx_ln”) ---- except the hit that was used to get a residuals: (“dx_ln_1”) -- “nonlinearity” correction was done for x_w values: ( “x_corr”)

  8. Hit position reconstruction; nonlinearity correction hit position (reconstructed-simulated) before and after correction x_w in “pad coordinate system”, cm Pad size: 2x6 mm2, P10, Ar+CO2 Pad size: 3x5 mm2 (x_w – x_simul), cm

  9. Different variants of hit position reconstruction 2 x 6 mm2 3 x 5 mm2 - (x_corr – x_simul) - (x_w – x_simul) P10 - (x_gf – x_simul) Ar+CO2

  10. Sigma of gauss fit (reconstructed-simulated), mm.Drift: 0-15 cm, Slope: +/- 16 deg

  11. Simulation – Data comparison, P10, “Canada” Resolution in X, mm Pad size 2.x6. mm² Experimental data “gauss fit” Pad size 3.x5. mm² “nonlinearity correction” Drift distance, cm

  12. Simulation – Data comparison, Ar+CO2(10%), “Canada”. factor ~2 smaller transfer diffusion and factor ~3 smaller drift speed compare with P10 Resolution in X, mm Pad size 2x6 mm² Gauss fit Experimental data Pad size 3x5 mm² nonlinearity correction Drift distance, cm

  13. Number of active pads and Q per cluster for different variants. 2x6 mm² 3x5 mm² 2x6 mm² 3x5 mm² P10 Ar+CO2

  14. Hit resolution as a function of a slope ( in xy ) P10, pad size 2x6 mm2 3x5 mm2

  15. Hit reconstruction resolution in a drift direction. Pad size 2x6 mm2 3x5 mm2 P10 Ar+CO2

  16. Space resolution as a function of a pad size (in RΦ direction) for 40. cm max drift distance, “custom” FEE and 20.ns time-bin Sigma of gauss fit, cm. hit position in RPhi (simulated-reconstructed) Sigma, cm, gauss fit (x_simul – x_reco) HIJING, CH4 CERN TPC+GEMs: measurement – 0.0178 simulation – 0.0169 One track/event CF4(10%)+Ar ( in brackets: x-y line fit using 5 pad rows, gaussian fit (x0-x0 simulated)) Pad size, cm

  17. Comparison of the hit reconstruction precision for rectangle and chevron pad shapes. Pad size: 1.0x0.2 cm², 10 saws in a case of chevron shape Hit position (along pad-row), cm, simulated Track slope, deg chevron pads rectangle pads Xsimul – Xreco, cm Xsimul – Xreco, cm

  18. Space resolution, one pad-row, Chevron Pad structure: 1.0x0.2 cm – 10 saws. After slope correction Before Slope, deg. Slope, deg. Sigma, gauss fit: 0.032 cm 0.006 cm dX, cm dX, cm

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