Electron-Photon showers in CORSIKA 8
PROPOSAL Update: Dortmund Group
- Interpolation issues arising at a non-differential kink, the transition between the relative and absolute cut of the energy loss, resulting in particles propagating backward in certain conditions. New Interpolation methods have been developed using boost and Eigen as an external package (https://github.com/MaxSac/cubic_interpolation). They solve this issue, but are not yet included in CORSIKA!
- Short recap on energy cuts: there are cuts on the minimum particle energy to propagate and further cuts on the minimum energy of an energy loss to be considered as stochastic and not averaged out in continuous losses. When comparing CORSIKA8 with other EM-Shower simulation tools, the same energy cuts need to be applied.
- Interesting for the radio emission is the continuous energy loss between two stochastic interaction points, while for some processes using the PROPOSAL output assume no continuous loss (https://gitlab.ikp.kit.edu/AirShowerPhysics/corsika/-/issues/280). A trade-off between the maximum step size or the energy loss needs to be figured out. Further discussions should take place in the issue-link.
- Plans to present the technical part of PROPOSAL in CORSIKA at CHEP and the physical part at ICRC. ICRC contributions should be listed here (https://gitlab.ikp.kit.edu/AirShowerPhysics/corsika/-/wikis/ICRC2021).
EM-Shower Comparisons: Juan Ammerman Yebra
- Simulated 50 EM-Showers with an initial 100 TeV electron through Air (no Argon) with homogeneous density and a threshold on the particle energy of 20 MeV using ZHS, AIRES and C8
- Regarding the longitudinal profile, C8 systematically produces fewer particles; while the number of photons is close to the other two, there is just half of the number of electrons and positrons. Besides, there is a spike in C8 at the first bin.
- The charge excess, important for the radio emission, differs between all simulation tools. There is just a small charge excess in C8, which doesn't increase as the shower develops. The excess in ZHS is higher compared to C8 by up to a factor of 10, while the excess in AIRES is up to 50% higher compared to ZHS. Zas mentioned, that 60% of the charge excess originates from Compton processes.
- Comparing the energy distributions of C8 and ZHS before and after the Xmax: For photons, the low and high energy regions agree, while C8 is systematically lower at medium energies. Positrons and electrons are systematically lower for all energies.
- Regarding the longitudinal profile with a higher threshold on the particle energy (10 GeV) comparing ZHS, C7, C8: the number of photons and electrons/positrons agrees, also all three show no charge excess, as expected due to the higher particle threshold.
- Further checks regarding the energy deposited at certain depths, dE/dX, are needed to consider also the continuous energy losses.
- Also all simulations should have the same energy cuts on the energy loss needs, which has not been checked.
- The run time for ZHS and AIRES are in the range of a couple of minutes while CORSIKA 7 and 8 both require 10-20 minutes.
The next EM-Shower meeting will be in 4 weeks.