Microscopic 8-quark study of the antikaon nucleon nucleon systems

We study the possibility to bind eight quarks in a molecular hadronic system composed of two nucleons and an antikaon, with the quantum numbers of a hexaquark flavour, in particular with strangeness -1, isospin 1/2, parity -, baryonic number 2 and two possible spins, 0 or 1. These exotic hadrons are motivated by the deuteron, a proton-neutron boundstate, and by the model of the Lambda(1405) as an antikaon proton boundstate. We discuss the possible production of this hadron in the experiments which are presently investigating hot topics like the Theta+ pentaquark or the K- deeply bound in nuclei. The K- N interactions and the coupling to other channels are computed microscopically from a confining and chiral invariant quark model resulting in local plus separable Gaussian potentials. The N N interactions used here are the state of the art Nijmegen potentials. The binding energy and the decay rate of the K- N and K- N N systems are computed with configuration space variational methods. The only systems that bind with our microscopic interaction are the K- N in the I=0 channel and the K- N N in the S=0 channel.Comment: 5 pages, 5 figures (1 new and 2 updated), more detailed study of binding with a small parameter increase, and an algebraic correction, submitted to Physical Review

Exotic pentaquarks, crypto-heptaquarks and linear three-hadronic molecules

In this talk, multiquarks are studied microscopically in a standard quark model. In pure ground-state pentaquarks the short-range interaction is computed and it is shown to be repulsive, a narrow pentaquark cannot be in the groundstate. As a possible excitation, an additional quark-antiquark pair is then considered, and this is suggested to produce linear molecular system, with a narrow decay width. This excitation may be energetically favourable to the p-wave excitation suggested by the other pentaquark models. Here, the quarks assemble in three hadronic clusters, and the central hadron provides stability. The possible crypto-heptaquark hadrons with exotic pentaquark flavours are studied.Comment: 8 pages, 3 tables, talk presented at the International Workshop PENTAQUARK04 July 20-23, 2004, SPring-8, Japa

Quark running mass and vacuum energy density in truncated Coulomb gauge QCD for five orders of magnitude of current masses

We study in detail the effect of the finite current quark mass on chiral symmetry breaking, in the framework of truncated Coulomb gauge QCD with a linear confining quark-antiquark potential. In the chiral limit of massless current quarks, the breaking of chiral symmetry is spontaneous. But for a finite current quark mass, some dynamical symmetry breaking continues to add to the explicit breaking caused by the quark mass. Moreover, using as order parameter the mass gap, i. e. the quark mass at vanishing moment or the quark condensate, a finite quark mass transforms the chiral symmetry breaking from a phase transition into a crossover. For the study of the QCD phase diagram it thus is relevant to determine how the current quark mass affects chiral symmetry breaking. Since the current quark masses of the six standard flavours u, d, s, c, b, t span over five orders of magnitude from 1.5 MeV to 171 GeV, we develop an accurate numerical method to study the running quark mass gap and the quark vacuum energy density from very small to very large current quark masses.Comment: 24 pages, 5 figures, 3 table

The Pentaquarks in the Linear Molecular Heptaquark Model

In this talk, multiquarks are studied microscopically in a standard quark model. In pure ground-state pentaquarks the short-range interaction is computed and it is shown to be repulsive. An additional quark-antiquark pair is then considered, and this is suggested to produce linear molecular system, with a narrow decay width. The quarks assemble in three hadronic clusters, and the central hadron provides stability. The possible crypto-heptaquark hadrons with exotic pentaquark flavours, with strange, charmed and bottomed quarks, are predicted.Comment: 6 pages, 3 tables, talk presented as the Eighth Workshop on Non-Perturbative Quantum Chromodynamics 7-11 June 2004, Paris, proceedings edited by B. Muller, Chung-I Tan and Y. Gabellin