1. Transmission and Reflection of Electrons using GEANT3 Angus Comrie (University of Cape Town, SA-CERN) Supervisor: Karel Safarik Kinetic Energies of 100keV to 1MeV, Aluminium & Beryllium foils of thickness <500 micron

2. Background Heavy flavour mesons (D 0 etc) have small (100μm) impact parameters Produced δ-rays may interfere with pixel detector’s cluster algorithm, produce “charm candidates” by fake impact parameter Many more tracks than real charm events

3. Expected δ-ray energy distribution

4. 1GeV Pion in 500μm Foil Δ-ray Kinetic Energy (T 0 ) # of δ-rays with T>T 0 (per track) Emission Angle Range in Beryllium Range in Aluminium 0.1 MeV7×10 -3 70°90μm70μm 1.0 MeV7 ×10 -2 45°3mm2mm Non-negligible range in both Be & Al

5. Simulation Setup ROOT VirtualMC GEANT3 (GEANT4 comparison soon) Z<0: Reflected Z>0: Transmitted

6. Calculated Quantities Transmission/Reflection Number Coefficients T N, R N – T N can rise above 1 (additional e - knocked on by δ-rays) Energy Spectra, E av, E p Transmission/Reflection Energy Coefficients T E, R E Angular Distribution Plot in (z/r 0 ) for energy-independent results (where r 0 is mean electron range in medium)

7. Reference Results

9. Transmission Coefficients (Al) Errors are not show as they are smaller than points (1%)

10. Transmission Coefficients (Be)

11. Reflection Coefficients (Al)

12. Closer to theoretical approximation Agrees for small (z/r 0 )

13. Conclusion T N similar to MC results – Deviates at larger (z/r 0 ) – Differs by up to 20% for Be & 15% for Al R N totally off below 1MeV – Possibly fixed in later version of GEANT4

14. Further Work Short Term (Next week): – Compare with GEANT4 simulation – Tweak simulation parameters Long Term: – Full simulation of production and propagation of δ-rays in detector – Simulate detector response