photo-nuclear interaction with sibyll

assigned to @riehn

@msackel For the hadronic interaction of photons with nuclei, once you have the cross section you can use Sibyll to create the hadronic final state.

Thus, we do not need PROPOSAL to create a special object (nuclear collision) or so, we need only the cross section. CORSIKA8 will take care of the rest.

Felix, I know Sibyll can do the photo-hadronic, but are there "better" choices (or at least valid alternatives), too? E.g. phojet, DPMJET, ... ??

Sibyll does not do photo-hadronic interaction but it can do interactions of

\rho

which are part of the 'hadronic photon'. More complete

\gamma+p

interactions are provided by DPMjet.
In the context of C7, as far as I know, only approximations like using

\rho

or

\pi

as stand in for the photons are used.

PROPOSAL is a priori only interested in the total cross section for photoabsorption of virtual photons, because that is what we need for the photonuclear interaction of leptons. The structure functions we use internally contain directly this total cross section. But to break this down into definite final states (in contrast to the total cross section via the optical theorem) requires additional modeling.

Using a ρ meson as proxy for the photon, as was done in the first vector meson dominance papers a very long time ago, would obviously be an approximation, but for electrons, photonuclear interaction is only a small part of the energy loss of about 1e-4; therefore electromagnetic showers should not be noticeably influenced by the way we treat this.

For muons this might be different, since photonuclear interaction contributes about 10% of the total energy loss at multi-TeV energies (and the fraction is slowly rising at larger energies). Also, the virtuality of photons is higher, since the minimum virtuality is proportional to the lepton mass squared. However, the ρ as lightest vector meson should describe at least a significant amount of the events.

I think using ρp -- or γp, if available -- to determine the final state is a viable way to solve this problem.

added EM Physics labels

mentioned in merge request !430 (merged)

mentioned in commit 8a317705

closed with merge request !430 (merged)