Are the anti-charmed and bottomed pentaquarks molecular heptaquarks?

Abstract

I study the charmed $uudd\bar c$ resonance D*p (3100) very recently discovered by the H1 collaboration at Hera. An anticharmed resonance was already predicted, in a recent publication mostly dedicated to the S=1 resonance Theta+(1540). To confirm these recent predictions, I apply the same standard quark model with a quark-antiquark annihilation constrained by chiral symmetry. I find that repulsion excludes the D*p (3100) as a $uudd\bar c$ s-wave pentaquark. I explore the D*p (3100) as a heptaquark, equivalent to a N-pi-D* linear molecule, with positive parity and total isospin I=0. I find that the N-D repulsion is cancelled by the attraction existing in the N-pi and pi-D channels. In our framework this state is harder to bind than the Theta+ described by a k-pi-N borromean bound-state, a lower binding energy is expected in agreement with the H1 observation. Multiquark molecules N-pi-D, N-pi-B* and N-pi-B are also predicted.