Are the Theta+(1540), Xi--(1860) and D*-p(3100) Pentaquarks or Heptaquarks?

Abstract

We study the Theta+(1540) discovered at SPring-8. We apply Quark Model techniques, that explain with success the repulsive hard core of nucleon-nucleon and kaon-nucleon exotic scattering, and the short range attraction present in pion-nucleon and pion-pion non-exotic scattering. We find a K-N repulsion which excludes the Theta+ as a K-N s-wave pentaquark. We explore the Theta+ as a crypto-heptaquark, equivalent to a K-pi-N borromean boundstate, with positive parity and total isospin I=0. The attraction is provided by the pion-nucleon and pion-kaon interactions. The other candidates to pentaquarks Xi--(1860), observed at NA49, and D*-p(3100), observed at H1, are also studied as linear molecular heptaquarks.