On the scalar meson exchange in 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 also subject to a linear confinement. We study how the spectrum
evolves when the strength of the scalar meson exchange increases. Our
results are relevant to the long-standing problem of the relative
position of the first positive-parity (Roper resonance) and the first
orbitally excited states in the baryon spectrum.