Baryons in a chiral constituent quark model

Abstract

In the low-energy regime light and strange baryons should be considered as systems of constituent quarks with confining interaction and a chiral interaction that is mediated by Goldstone bosons as well as by vector and scalar mesons. The flavor-spin structure and sign of the short-range part of the spin-spin force reduces the $SU(6{)}_{FS}$ symmetry down to $SU(3{)}_F\times SU(2{)}_S$, induces hyperfine splittings and provides correct ordering of the lowest states with positive and negative parity. There is a cancellation of the tensor force from pseudoscalar- and vector-exchanges in baryons. The spin-orbit interactions from $\rho$-like and $\omega$-like exchanges also cancel each other in baryons while they produce a big spin-orbit force in NN system. A unified description of light and strange baryon spectra calculated in a semirelativistic framework is presented. It is demonstrated that the same short-range part of spin-spin interaction between the constituent quarks induces a strong short-range repulsion in $NN$ system when the latter is treated as $6Q$ system. Thus one can achieve a simultaneous understanding of a baryon structure and baryon-baryon interaction in the low-energy regime.

13 pages, Lecture given at 4th Petersburg Winter School on Theoretical Physics in memory of V.N. Gribov

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