Implement thinning algorithms

Weights are already handled by particles, but we have not yet implemented any thinning algorithms. This is a typical SecondariesProcess, should be super straightforward to add.

changed milestone to %Full physics demonstratror

added Development label

assigned to @mreininghaus

created branch 445-implement-thinning-algorithms to address this issue

mentioned in merge request !466 (merged)

I got a simple question: what is different between the new "thinning" and the already haved "energy cut and production threshold"? My understanding is:

• We do "energy cut" in SecondaryProcess to remove low energy particle in the SecondaryView.
• We do "production threshold" in physics table (by adding threshold in differential cross-section) so that the low energy particles are not produced. (Currently only supported by PROPOSAL I guess)

Could you briefly explain what "thinning" is and why we need that?

Please have a look at https://doi.org/10.1016/S0927-6505(00)00158-4. for instance.

Thanks for providing the reference. Now I got some flavor of that.

• "Thinning" is to represent the shower by fewer tracks via weighting method while keeping enough statistics for future analysis and reconstruction.

mentioned in commit 72ece5d8

closed with merge request !466 (merged)