The Ioffe current constants for the proton and Roper resonance are evaluated using a linear confining potential model parametrized to reproduce the proton magnetic moment, spin, and energy. The three-body Dirac equation, for the ${(1/2\mathrm{}}^{+}{)}^3$ positive parity configuration, is solved in hypercentral approximation. Quark masses of the order of 9 MeV are needed to reproduce the proton magnetic moment. When the proton rms charge radius and magnetic moment are reproduced, the Roper has an Ioffe coupling constant about 25% larger than the proton.

• Received 10 January 1997

DOI:https://doi.org/10.1103/PhysRevC.56.551