repair EPOS interface

The following discussion from !387 (merged) should be addressed:

• @rulrich started a discussion: (+3 comments)

  @riehn this MR is now finished. EPOS is also fixed. I added a few more unit tests for COMBoost and it looks ok so far. The corsika-modules/epos/check.cpp was also updated to run CRMC collisions. It would be great, if you could run some tests!

changed milestone to %Interaction interface overhaul.

added Bug Hadronic labels

I showed the plots to Tanguy, and he speculated it could be a particle ID conversion mishap. The "wrong" energies are quite rare, if you look in detail. Most of the distribution might just be OK.

Tanguy also said: we should run EPOS in c.m.s. mode. That is more general and numerically more robust.

I was also going to suggest to change EPOS to cms mode. The lab momenta are passed as float so there is a slight shift in the invariant mass due to the loss of significant digits. In other words the kinematic mass of the incoming particle drifts since it is m2 = (e2 - p**2). Or that was my theory at least.

eg. for 13TeV pp interactions there is a 3 GeV difference between Plab per nucleon in C8 and Epos (Pnll)

[corsika_epos_Interaction:trace   (InteractionModel.inl:170)] initialize event in lab. frame! Plab per nuc=90059363.6369589 GeV
[corsika_epos_Interaction:trace   (InteractionModel.inl:183)] inside EPOS: Ecm=-1, Elab=-1, Pnll=90059360

mentioned in issue #443 (closed)

Here is the output from one event at 13TeV in debug level 4. epos_1event_13TeV_pp.out

The issue: spectra in px,py,pz and energy in Epos:

Thanks ... did you use ish=4, it seems that there is more output than I thought ... any way, the CORSIKA8 output is a bit cryptic for me, it is much easier for you to understand the EPOS output since you see that there is a long list of particles (may be you could find an event with a smaller multiplicity ;-) ) where you get everything. May be you can easily compare what you get in and what gets out. Also a first test could be to do some plots in the CMS frame without any boost where you could see that everything should be OK ?

Hi Tanguy, yes this is ish=4. I will see if I can find a smaller event and try to change to use EPOS in CMS..

Changing to CoM seems to have done the trick. No clue what was wrong in the end.

And here the energy spectra of the three models:

Remaining differences can be explained by different particles being stable.

changed title from Follow-up from "Hadronic model interface overhaul" to repair EPOS interface

created branch 467-repair-epos-interface to address this issue

marked this issue as related to #443 (closed)

marked the checklist item @rulrich started a discussion: (+3 comments) as completed

mentioned in merge request !407 (merged)

Nice ... these spectra are not suppose to be the same anyway ! May be there was some interference between the different boost. Now it looks much better :-).

Does it mean EPOS is in C8 now ?

Yes EPOS is in C8 now, although I'd wait with the celebration until @mreininghaus ran the first showers Ah also I didn't test nuclei and decay configuration may have to be revisited but definitely CRMC-style hadron-hadron interactions work.

Very nice! Thanks!!

mentioned in commit 785332c9

closed with merge request !407 (merged)