Scalar meson exchange and the baryon spectra
  We explore the role of a scalar meson exchange interaction between quarks in a semirelativistic constituent quark model where the quarks are subject to a linear confinement. We search for a variational solution and show that the gap between the N=1 band and the ground state N=0 band increases with the strength of the scalar meson exchange interaction potential. This result has good implications on the description of the low-lying baryon resonances, especially on the Roper vs. negative parity resonances ordering. 
P. Stassart (U. of Liege), Fl. Stancu (U. of Liege) and J.-M. Richard   (U. Joseph Fourier, Grenoble)