Kaon mass produced by Pythia8 hadronization is incompatible with later Geant4 processing

[nusense]

[copying a discussion from slack into a GitHub issue]

@mroda88 wrote:
Hi all. Wes found that the kaons produced by the Pythia8 hadronisation have the mass of the Kaons set in Pythia8 and not in our configuration. This is possibly ok, if it wasn't for the value of the mass they are using, it's a particularly low value: 497.61 MeV. When passed to Geant4 these particles cannot be decayed because the mass that G4 is using (and it is hardcoded) is 497.614 MeV. which is higher than the mass we provide.

I thought everyone should be aware of the issue

@candreop wrote:
Maybe good idea for consistency to run a series of pythia.particleData.m0(code, value) at Pythia init, synchonizing it with our PDGLibrary

@nusense wrote:
I'd have to give it some thought, but because we switched over to having Pythia8 be wrapped in a Singleton for our use, this might not be that hard to implement at the initial instantiation. Assuming that our PDG table is filled before the first Pythia8 use.

[nusense]

Here's a look at some of the masses of the most basic particles as seen by various codes and the PDG group