For electron-positron pair production by leptons, so far, only the rho sampling (energy distribution between the produces particles) based on the differential cross section by Kelner (KKP) has been implemented (and is also the default).
However, for electrons and positrons as initial particles, there is a dedicated differential cross section called ForElectronPositron. Since both the KKP and ForElectronPositron parametrizations have a similar structure, it was trivial to combine the secondaries calculator using a template class.
This is more elegant, and allows us to offer dedicated calculators for the different initial particles.
There is also a significant difference when using the different parametrizations, for example for electrons. This can be seen in this plot, where the rho sampling for initial electrons is shown for the two different parametrizations:
What might be discussed: Which secondaries calculator should be used as the deafult? We provide one "default" for every interaction type.
The perfect solution would be to add different default for different initial particles, but this is out of the scope of this PR.
So for now, we should decide on either ForElectronPositron or KKP as the default.
For now, I decided to use ForElectronPositron as the default, because for all other secondary calculators, we provide the default calculators that are valid for electron/positrons.
What might speak against this: This production process is actually only relevant for muons.
For electron-positron pair production by leptons, so far, only the rho sampling (energy distribution between the produces particles) based on the differential cross section by Kelner (
KKP) has been implemented (and is also the default).However, for electrons and positrons as initial particles, there is a dedicated differential cross section called
ForElectronPositron. Since both theKKPandForElectronPositronparametrizations have a similar structure, it was trivial to combine the secondaries calculator using a template class. This is more elegant, and allows us to offer dedicated calculators for the different initial particles.There is also a significant difference when using the different parametrizations, for example for electrons. This can be seen in this plot, where the rho sampling for initial electrons is shown for the two different parametrizations:
What might be discussed: Which secondaries calculator should be used as the deafult? We provide one "default" for every interaction type. The perfect solution would be to add different default for different initial particles, but this is out of the scope of this PR. So for now, we should decide on either
ForElectronPositronorKKPas the default. For now, I decided to useForElectronPositronas the default, because for all other secondary calculators, we provide the default calculators that are valid for electron/positrons. What might speak against this: This production process is actually only relevant for muons.