Understanding physics settings

Dear Experts,

I want to study muon and antimuon production in heavy ion collisions(4GeV/n). I want to understand how to set physics settings correctly for simulation. As far as i know main source of muon production is leptonic decays of pions/kaons. So in physics i found Decays options which treats this kind of decays. What else i should set(PAIRBREM, PHOTONUC, MYRQDM…)? And how to understand why and how i should do that?

Hi, generally speaking, FLUKA does not require you to activate physics processes, apart from a few exceptions, as mostly recalled here. In particular, the options you mention are all irrelevant to your purposes (leptonic decay of mesons is on by default).
The only crucial point, as dealing with heavy ion collisions, is the use of DPMJET (and RQMD for reactions below 5 GeV/n with target at rest that may be your case if you refer to beam-target collisions rather than beam-beam collisions), which implies not to introduce cards but to run the flukadpm executable (rather than the standard fluka) or to generate your own executable by means of the ldpmqmd linking script (also available in the Compile tab of Flair). Without DPMJET (or RQMD where applicable), no heavy ion nuclear reaction is actually simulated (except on hydrogen, where it becomes a proton-nucleus reaction), then no meson is generated and no muon is produced.
In case of beam-beam collisions (to be simulated by means of the SPECSOUR card), one shall also remember to add a PHYSICS card with SDUM=LIMITS, to properly initialize DPMJET with the maximum nucleon momentum in the centre-of-mass system.
Also, depending on the ion charge and energy, electromagnetic dissociation may be a relevant process, to be explicitly activated by the PHYSICS card with SDUM=EM-DISSO, as indicated in the above lecture.
Finally, PHOTONUC is required both for performing nuclear interactions of photons and muon pair production by photons (with different SDUMs), but I fail to see either of the two processes as playing a role in your problem.

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Dear Francesco,

Thank you very much! Your answer helped me a lot!