sPHENIX discussion of physics

["Perepelitsa, Dennis" <dvp AT bnl.gov>]

Dear sPHENIX colleagues,

This month, I’ve been reading a paper which does not contain a physics measurement, but is rather focused on modeling for jet physics:

Aguilar et al, PYTHIA8 underlying event tune for RHIC energies, INSPIRE link, pub. PRD

This paper tunes parameters in Pythia related to how the generator deals with multi-patron interactions (MPIs) and color reconnection (CR) to a variety of STAR and PHENIX data. The data include charged pion and Drell-Yan cross-sections, properties of the underlying event properties, and groomed jet observables.

The RHIC data appear to favor rather different values for these MPI/CR parameters than those used by some existing popular tunes which are largely driven by LHC data. In the end, the authors produce a new “Detroit” tune for RHIC energies.

For me personally, I was surprised to see that Pythia parameters related to “soft physics” (UE production, hadronization) have as big an effect as they do on groomed jet observables - which are designed to be less sensitive to the details of the soft processes.

As we move closer to producing simulations to support real physics analyses in data, we may want to look more closely at their tuning. Any thoughts?

Dennis