transmission and reflection of electrons using geant3 angus comrie (university of cape town,...
TRANSCRIPT
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
Background• Heavy flavour mesons (D0 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
Expected δ-ray energy distribution
1GeV Pion in 500μm Foil
Δ-ray Kinetic Energy (T0)
# of δ-rays with T>T0 (per track)
Emission Angle
Range in Beryllium
Range in Aluminium
0.1 MeV 7×10 -3 70° 90μm 70μm
1.0 MeV 7 ×10 -2 45° 3mm 2mm
•Non-negligible range in both Be & Al
Simulation Setup
• ROOT VirtualMC• GEANT3 (GEANT4 comparison soon)
Z<0: Reflected
Z>0: Transmitted
Calculated Quantities
• Transmission/Reflection Number Coefficients TN, RN
– TN can rise above 1 (additional e- knocked on by δ-rays)
• Energy Spectra, Eav , Ep
• Transmission/Reflection Energy Coefficients TE, RE
• Angular Distribution• Plot in (z/r0) for energy-independent results (where
r0 is mean electron range in medium)
Reference Results
Transmission Coefficients (Al)Errors are not show as they are smaller than points (1%)
Transmission Coefficients (Be)
Reflection Coefficients (Al)
•Closer to theoretical approximation•Agrees for small (z/r0)
<cos
(θ)>
Conclusion
• TN similar to MC results – Deviates at larger (z/r0)– Differs by up to 20% for Be & 15% for Al
• RN totally off below 1MeV– Possibly fixed in later version of GEANT4
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