  The nucleon-nucleon problem is studied as a six-quark system in a
nonrelativistic chiral constituent quark model where the Hamiltonian contains a
linear confinement and a pseudoscalar meson (Goldstone boson) exchange
interaction between the quarks. This hyperfine interaction has a long-range
Yukawa-type part, depending on the mass of the exchanged meson and a
short-range part, mainly responsible for the good description of the baryon
spectra.
