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Geant4 Low Energy Polarized Processes

Geant4 Low Energy Polarized Processes. Gerardo Depaola * Francesco Longo +. * National University of Córdoba (Argentina) + University of Ferrara and INFN (Italia). Talk Outline. Compton Effect · Angular Distribution for Scattered gamma. · Vector Polarization distribution.

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Geant4 Low Energy Polarized Processes

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  1. Geant4 Low Energy Polarized Processes Gerardo Depaola* Francesco Longo+ * National University of Córdoba (Argentina) + University of Ferrara and INFN (Italia)

  2. Talk Outline • Compton Effect · Angular Distribution for Scattered gamma. · Vector Polarization distribution. • Pair Production · Azimuthal distribution. • Effect of polarization · Asymmetric ratio.

  3. COMPTON SCATTERING The Klein Nishina cross section: Where, h0 : energy of incident photon. h : energy of the scattered photon.  : angle between the two polarization vector

  4. x A f e y C O Angles in the Compton Effect •  Polar angle •  Azimuthal angle •  Polarization vector x x f hn  A hn0 q a z O C y

  5. e’|| x e’ b Q x A hn e’^ x e O C Angular distribution Scattered Radiation compose of two components: e’|| and e’^respect to AOC plane

  6. Summing over the two direction the cross section can be write as: • Sample Methods implemented in G4LowEnergyPolarizedCompton class: • Integrating over  • Sample  • Theta - Energy Relation Energy • Sample of  fromP() = a (b – c cos2) distribution

  7. Results • Class inserted in next G4 release • To be compared with Experimental results • Scattered Polarization  distribution obtained with the class

  8. Scattered Photon Polarization  is obtain from cos  = cos  N and  is sample from Klein Nishina cross section

  9. Test of the distribution: a) low energy b) high energy The distribution function is: where and  = h / h0. Low energy: ho << mc2 => hho =>  =1 => a = 0 the distribution reduces to the Thompson distribution => the probability that the two polarization vectors are perpendicular is zero. High energy: small  => hho => equal to low energy high : it is possible to demonstrate that b/(a+b) ->0, so in this case the distribution tend to be isotropic.

  10. Results Scalar product between the two polarization vectors for three different energies. Upper histograms: Low polar angle  Lower histograms:High polar angle  100 keV 1 MeV 10 MeV These distributions are in agreement with the limits obtained previously.

  11. PAIR PRODUCTION Cross Section:

  12. z k p+ p- x  + -   y Angles occurring in the pair production

  13. Azimuthal Distribution of a Pair Created by 100 MeV Photon.

  14. Effects of polarization Asymmetric Ratio nº of pairs contains in plane parallel to the vector polarization to nº of pairs perpendicular Asymmetric ratio for pair production

  15. Asymmetric ratio for Compton scattering Polar aperture

  16. Polar aperture

  17. In progress • Test the Compton class with experimental data. • Include the binding effect in the Compton class. • Build the class for pair production. • Develop a class for : • 1) Rayleig scattering • 2) Photoelectric effects

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