eef van beveren (unregistered)
In our analysis of meson-meson scattering data, see e.g. here and here and many articles later on, we came aware of two constants of Nature (same for all flavors), namely the internal mesonic oscillation frequency of 190 MeV and the minimum energy of 3P0 quark-pair creation.
The latter constant was never advertised by us in terms of a mass, but, instead, in terms of a radius. The reason was that my collaborators, back in the late seventies, did not want to publish a light mass which had no observation associated with it.
I did not forget about the mass, even used it in my computer code which translated it into the distance.
Besides the explanation of several new resonances I found, in collaboration with George Rupp, four different types of enhancements:
Those which can be related to the quark-antiquark spectrum.
Resonances which are dynamically generated via the 3P0 quark-pair-creation mechanism.
Non-resonant threshold enhancements.
Non-resonant enhancements which occur by depletion.
We also predicted some new resonances.
Only a few years ago, I came aware of indications for a possible quantum of a mass of about 38 MeV which corresponds to the quark-pair-creation mechanism used by us.
When, I had sufficient material, I decided to publish it with George Rupp.