Unified gravi-strong model for 3-quark states and a solution to the ‘proton spin crisis’

We discuss the unified gravi-strong (UGS) model for 3-quark bound states based on Yang–Mills gravity and a new confining quarkdynamics, both of which are formulated using space–time translation ([Formula: see text]) gauge symmetry. The model postulates that the properties of a baryon can be obtained by treating it as two quarks forming an S-like quantum state in a linear potential generated by the third quark at the core of the baryon, and the third (core) quark in a quadratic potential generated by the first two quarks. The mass of the baryon is simply the sum of the energies of the three quarks, which can be obtained analytically from the Dirac Hamiltonians. The UGS model includes just three unknown constants in the quark potentials, two of which seem to be related to the isospin of the core quark, and one that depends on the baryon sub-spectrum. It can predict the masses of over 120 baryons to within roughly 20% of their experimentally measured or expected values, including a value of 0.6 MeV for the difference between the neutron and proton masses. The interquark interactions of the UGS model also provide a natural explanation for why the experimentally measured mass of a baryon is so much larger than the total inferred masses of the quarks that form it. In addition, the structure of two quarks forming an S-like quantum state around a third core quark suggests a possible solution to the ‘proton spin crisis’. We suggest an experimental test of the proposed core structure of a proton using deep inelastic muon–proton scattering at high energies.