The Theta+ (1540) as an overlap of a pion, a kaon and a nucleon

Abstract

We study the very recently discovered ${\Theta }^{+}$ (1540) at SPring-8, at ITEP and at CLAS-Thomas Jefferson Lab. We apply the same RGM techniques that already explained with success the repulsive hard core of nucleon-nucleon, kaon-nucleon exotic scattering, and the attractive hard core present in pion-nucleon and pion-pion non-exotic scattering. We find that the K-N repulsion excludes the Theta+ as a K-N s-wave pentaquark. We explore the Theta+ as heptaquark, equivalent to a N+pi+K borromean boundstate, with positive parity and total isospin I=0. We find that the kaon-nucleon repulsion is cancelled by the attraction existing both in the pion-nucleon and pion-kaon channels. Although we are not yet able to bind the total three body system, we find that the Theta+ may still be a heptaquark state.

Comments: 5 pages, 3 figures, 1 table, contribution to the X International Conference on Hadron Spectroscopy, HADRON 2003, August 31 - September 6, 2003, Aschaffenburg, Germany