Gamma Conversion macros:

gamma.mac - tests of the 5D gamma -> e+ e- conversion model G4BetheHeitler5DModel
gamma2mumu.mac - tests of the 5D gamma -> mu+ mu- conversion model G4BetheHeitler5DModel

All discrete processes are inactivated (see macro), so Gamma Conversion is 'forced'.

HISTOGRAMS

10 : Open Angle (rad)* E gamma (MeV).

The most probable value of the e+ e- pair opening angle multiplied by the photon energy is 1.6 rad*MeV and 338 rad*MeV in case mu+ mu- pair. See: Olsen, Phys. Rev. 131 (1963) 406. See also: Fig. 7 of arXiv:1802.08253 and Fig. 6 arXiv:1910.12501.

11 : Log10 ( recoil momentum).

The distribution of the recoil momentum is described by Jost, Phys. Rev. 80 (1950) 189 (no form factor). See also Fig. 2 of Astroparticle Physics 88 (2017) 60.

12 : Phi recoil.
13 : Phi positron.

For linearly polarized incident photons, the distributions should show a sinusoidal shape with period 180°, for non polarized incident photons, the distribution of azimuthal angles should be flat.

14 : Asymmetry 2 * cos(phi_+ + phi_-).

For a photon propagating along x, polarized along y, the average value of ( 2.0 * cos(phi_+ + phi_-) ), provides a measurement of the polarization asymmetry, A. Eq. (12) of Nucl. Instrum. Meth. A 729 (2013) 765 The azimuthal angle of the event defined as the bisector angle of the azimuthal angles of the positron and of the electron, (phi_+ + phi_-)/2, provides the optimal measurement of the asymmetry Astroparticle Physics 88 (2017) 30.

For high-energy photons (E >> 20 MeV), the asymptotic expression for A can be used for comparison. Boldyshev, Yad. Fiz. 14 (1971) 1027, Sov.J.Nucl.Phys. 14 (1972) 576. See also eq. (13) of arXiv:1802.08253 Example : A ~ 0.17 at 100 GeV.

15 : E plus / E gamma.

x_+ = E plus / E gamma has a more-or-less flat spectrum that extends almost from 0. to 1. See Fig. 16 page 261 of "The Quantum Theory of Radiation", W. Heitler, 3rd edition, 1954.

16 : Phi of Gamma Polarization.

The phi of polarization vector after transformation into reference system defined by gamma direction (z) , gamma polarization (x).

UI COMMANDS

There are two commands to control G4BetheHeitler5DModel:

/process/gconv/conversionType itype
/process/gconv/onIsolated bool

The command:

/process/gconv/conversionType

Allow to force conversion on nuclear or electron The parameter values:

0 - (default) both triplet and nuclear conversion in proportion triplet/nuclear 1/Z
1 - force nuclear conversion
2 - force triplet

The command:

/process/gconv/onIsolated

Allow simulate conversion on isolated particles without screening The perimeter values:

false - (default) atomic electron screening
true - conversion on isolated particles

One more command for G4GammaConversionToMuons

To enable gamma to mu+ mu- conversion use command:

/process/em/max5DMuPairEnergy emax5D units

The conversion disabled by default, emax5D set to 0.0

The model tested for the energies about the threshold up to PeV range.