1. Oct. 22, 2003 - G.Lima1 Delving Deeper into Geant4 Guilherme Lima DHCal Meeting October 22, 2003

2. Oct. 22, 2003 - G.Lima2 Updates since last report Studied the spikes on the distributions of energy depositions in ECal and HCal absorbers Checked materials in subcomponents using geantino scans

3. Oct. 22, 2003 - G.Lima3 Spikes at Ecal absorber Is this a bug?

4. Oct. 22, 2003 - G.Lima4 Low energy EM Physics at play 69.5 keV 441 keV 511 keV 70 + 441 = 511!! E γ = 511 keV in e+e- annihilation Φ W = 69.5 keV ? (photoelectric effect in tungsten)

5. Oct. 22, 2003 - G.Lima5 Why is the E γ splitted sometimes? PE happens here e- γ PE energy deposition is assigned here in LCDG4 Cell boundary

6. Oct. 22, 2003 - G.Lima6 Spikes at Hcal absorber 511 keV 504 keV MIP peak 7.11 keV zoom in green

7. Oct. 22, 2003 - G.Lima7 Geantino scanning Purpose: compare radiation lengths (X 0 ) and interaction lengths (λ I ) to make sure that materials are the same in Mokka and LCDG4 No φ-dependence (cylindrical symmetry) θ- and track-length dependences are shown

8. Oct. 22, 2003 - G.Lima8 X 0 dependence on θ (SDJan03) Big discrepancies in the forward regions? Comparisons so far

9. Oct. 22, 2003 - G.Lima9 λ I dependence on θ (SDJan03) Big discrepancies in the forward regions? Comparisons so far

10. Oct. 22, 2003 - G.Lima10 X 0, λ I along track length at θ= 90°, φ= 90° HCal ECal Tracker VXD Muon Coil

11. Oct. 22, 2003 - G.Lima11 X 0, λ I along track length at θ=5°, φ=90° Last detector component

12. Oct. 22, 2003 - G.Lima12 X 0 differences at θ = 5°, φ = 90° Differences are quite small

13. Oct. 22, 2003 - G.Lima13 Comparing apples to apples… Geant version 4.5.2 (new server) Geometry (SDJan03, projective) Physics list: identical data files Range cuts (0.1mm) Same events are processed in both detector simulators (single particles: 50 GeV e, μ, π) input from binary stdhep file: θ = 90°, flat in φ Geant4 external data files not used Materials (some minor differences, should never give significant differences in results)

14. Oct. 22, 2003 - G.Lima14 Conclusions Peaks at Ecal and HCal absorbers are due to e+e- annihilation in association and photoelectric effect Materials in LCDG4 and Mokka are in very good agreement Some low-level discrepancies remaining in both ECal and Hcal need to be understood Should we go for Geant3 cross checks?

15. Oct. 22, 2003 - G.Lima15 Next steps Fix to energy contributions per cell (lcdg4) Further investigation on the origin of discrepancies Look at some complex physics processes Think about digitization (energies into ADC counts)