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0001 TestEm15 : gamma.mac gamma2mumu.mac
0002
0003 - gamma.mac -
0004 tests of the 5D gamma -> e+ e- conversion model G4BetheHeitler5DModel
0005 - gamma2mumu.mac -
0006 tests of the 5D gamma -> mu+ mu- conversion model G4BetheHeitler5DModel
0007
0008 All discrete processes are inactivated (see macro),
0009 so Gamma Conversion is 'forced'.
0010
0011 Histograms :
0012
0013 10 # Open Angle (rad)* E gamma (MeV)
0014 The most probable value of the e+ e- pair opening angle multiplied by the
0015 photon energy is 1.6 rad*MeV and 338 rad*MeV in case mu+ mu- pair.
0016 See: Olsen, Phys. Rev. 131 (1963) 406.
0017 See also: Fig. 7 of arXiv:1802.08253 and Fig. 6 arXiv:1910.12501.
0018
0019 11 # Log10 ( recoil momentum)
0020 The distribution of the recoil momentum is described by
0021 Jost, Phys. Rev. 80 (1950) 189 (no form factor).
0022 See also Fig. 2 of Astroparticle Physics 88 (2017) 60.
0023
0024 12 # Phi recoil
0025 13 # Phi positron
0026 For linearly polarized incident photons, the distributions should show
0027 a sinusoidal shape with period 180°, for non polarized incident photons,
0028 the distribution of azimuthal angles should be flat.
0029
0030
0031 14 # Asymmetry 2 * cos(phi_+ + phi_-)
0032 For a photon propagating along x, polarized along y,
0033 the average value of ( 2.0 * cos(phi_+ + phi_-) ),
0034 provides a measurement of the polarization asymmetry, A.
0035 Eq. (12) of Nucl. Instrum. Meth. A 729 (2013) 765
0036 The azimuthal angle of the event defined as the bisector angle
0037 of the azimuthal angles of the positron and of the electron,
0038 (phi_+ + phi_-)/2,
0039 provides the optimal measurement of the asymmetry
0040 Astroparticle Physics 88 (2017) 30.
0041
0042 For high-energy photons (E >> 20 MeV), the asymptotic expression for A
0043 can be used for comparison.
0044 Boldyshev, Yad. Fiz. 14 (1971) 1027, Sov.J.Nucl.Phys. 14 (1972) 576.
0045 See also eq. (13) of arXiv:1802.08253
0046 Example : A ~ 0.17 at 100 GeV.
0047
0048 15 # E plus / E gamma
0049 x_+ = E plus / E gamma has a more-or-less flat spectrum that extends
0050 almost from 0. to 1.
0051 See Fig. 16 page 261 of "The Quantum Theory of Radiation", W. Heitler,
0052 3rd edition, 1954.
0053
0054 16 # Phi of Gamma Polarization
0055 The phi of polarization vector after transformation into reference system
0056 defined by gamma direction (z) , gamma polarization (x).
0057
0058 UI commands:
0059
0060 There are two commands to control G4BetheHeitler5DModel:
0061
0062 /process/gconv/conversionType itype
0063 /process/gconv/onIsolated bool
0064
0065 The command:
0066 /process/gconv/conversionType
0067
0068 Allow to force conversion on nuclear or electron
0069 The parameter values
0070 0 - (default) both triplet and nuclear conversion in proportion triplet/nuclear 1/Z
0071 1 - force nuclear conversion
0072 2 - force triplet
0073
0074 The command:
0075 /process/gconv/onIsolated
0076
0077 Allow simulate conversion on isolated particles without screening
0078 The perimeter values:
0079 false - (default) atomic electron screening
0080 true - conversion on isolated particles
0081
0082 One more command for G4GammaConversionToMuons.
0083
0084 To enable gamma to mu+ mu- conversion use command:
0085
0086 /process/em/max5DMuPairEnergy emax5D units
0087 The conversion disabled by default, emax5D set to 0.0
0088
0089 The model tested for the energies about the threshold up to PeV range.
