Gabriele Cosmo
90 lines
3.0 KiB
Plaintext
90 lines
3.0 KiB
Plaintext
TestEm15 : gamma.mac gamma2mumu.mac
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- gamma.mac -
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tests of the 5D gamma -> e+ e- conversion model G4BetheHeitler5DModel
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- gamma2mumu.mac -
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tests of the 5D gamma -> mu+ mu- conversion model G4BetheHeitler5DModel
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All discrete processes are inactivated (see macro),
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so Gamma Conversion is 'forced'.
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Histograms :
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10 # Open Angle (rad)* E gamma (MeV)
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The most probable value of the e+ e- pair opening angle multiplied by the
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photon energy is 1.6 rad*MeV and 338 rad*MeV in case mu+ mu- pair.
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See: Olsen, Phys. Rev. 131 (1963) 406.
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See also: Fig. 7 of arXiv:1802.08253 and Fig. 6 arXiv:1910.12501.
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11 # Log10 ( recoil momentum)
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The distribution of the recoil momentum is described by
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Jost, Phys. Rev. 80 (1950) 189 (no form factor).
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See also Fig. 2 of Astroparticle Physics 88 (2017) 60.
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12 # Phi recoil
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13 # Phi positron
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For linearly polarized incident photons, the distributions should show
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a sinusoidal shape with period 180°, for non polarized incident photons,
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the distribution of azimuthal angles should be flat.
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14 # Asymmetry 2 * cos(phi_+ + phi_-)
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For a photon propagating along x, polarized along y,
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the average value of ( 2.0 * cos(phi_+ + phi_-) ),
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provides a measurement of the polarization asymmetry, A.
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Eq. (12) of Nucl. Instrum. Meth. A 729 (2013) 765
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The azimuthal angle of the event defined as the bisector angle
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of the azimuthal angles of the positron and of the electron,
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(phi_+ + phi_-)/2,
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provides the optimal measurement of the asymmetry
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Astroparticle Physics 88 (2017) 30.
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For high-energy photons (E >> 20 MeV), the asymptotic expression for A
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can be used for comparison.
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Boldyshev, Yad. Fiz. 14 (1971) 1027, Sov.J.Nucl.Phys. 14 (1972) 576.
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See also eq. (13) of arXiv:1802.08253
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Example : A ~ 0.17 at 100 GeV.
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15 # E plus / E gamma
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x_+ = E plus / E gamma has a more-or-less flat spectrum that extends
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almost from 0. to 1.
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See Fig. 16 page 261 of "The Quantum Theory of Radiation", W. Heitler,
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3rd edition, 1954.
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16 # Phi of Gamma Polarization
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The phi of polarization vector after transformation into reference system
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defined by gamma direction (z) , gamma polarization (x).
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UI commands:
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There are two commands to control G4BetheHeitler5DModel:
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/process/gconv/conversionType itype
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/process/gconv/onIsolated bool
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The command:
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/process/gconv/conversionType
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Allow to force conversion on nuclear or electron
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The parameter values
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0 - (default) both triplet and nuclear conversion in proportion triplet/nuclear 1/Z
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1 - force nuclear conversion
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2 - force triplet
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The command:
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/process/gconv/onIsolated
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Allow simulate conversion on isolated particles without screening
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The perimeter values:
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false - (default) atomic electron screening
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true - conversion on isolated particles
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One more command for G4GammaConversionToMuons.
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To enable gamma to mu+ mu- conversion use command:
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/process/em/max5DMuPairEnergy emax5D units
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The conversion disabled by default, emax5D set to 0.0
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The model tested for the energies about the threshold up to PeV range.
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