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

Oct. 22, 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

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

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

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

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

Oct. 22, 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

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

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

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

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

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

Oct. 22, G.Lima13 Comparing apples to apples… Geant version (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)

Oct. 22, 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?

Oct. 22, 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)