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The chiral SU (3) quark model is extended to include coupling between vector chiral field and quarks. By using this model, the phase shifts of NN scattering for different partial waves are studied. The results are very similar to those of the chiral SU(3) quark model calculation, in which one gluon exchange (OGE) plays dominate role in the short range part of the quark-quark interactions. Only in the 1 S0 case, the one channel phase shifts of the extended chiral SU (3) quark model are obviously improved.Key words: NN interaction, Quark Model, Chiral Symmetry. IntroductionAs is well known, in the light quark system the non-perturbative Quantum Chromodynamics (QCD) effect is important and not negligible. An effective approach to describe such effect can be made by introducing the coupling between the chiral fields and quarks, especially in studying the nucleonnucleon (N-N) interactions. A chiral SU (3) quark model [1,2] was proposed by generalizing the idea of the SU (2) σ model to the flavor SU (3) case. In the original chiral SU (3) quark model, the nonet pseuo-scalar meson exchanges and the nonet scalar meson exchanges are considered in describing the medium and long range parts of the interactions, and the one gluon exchange (OGE) potential is still retained to contribute the short range repulsion. By using this model, the energies of the baryon ground states, the N-N scattering phase shifts and the hyperon-nucleon (Y-N) cross sections can be reproduced reasonably. It seems that the repulsive core of the N-N interaction can be explained by the OGE and the quark exchange effect.Since last few years, Shen et al [3], Riska and Glozman [4,5] applied the quark-chiral field coupling model to study the baryon structure. They found that the chiral field coupling is also important in explaining the structure of baryons. Especially, the π field coupling leads to increase the weight of D

The isospin I = 0 and I = 1 kaon-nucleon S, P , D, F wave phase shifts are studied in the chiral SU(3) quark model by solving the resonating group method (RGM) equation. The calculated phase shifts for different partial waves are in agreement with the experimental data. Furthermore, the structures of the ∆K states with L = 0, I = 1 and I = 2 are investigated. We find that the interaction between ∆ and K in the case of L = 0, I = 1 is attractive, which is not like the situation of the N K system, where the S-wave interactions between N and K for both I = 0 and I = 1 are repulsive. Our numerical results also show that when the model parameters are taken to be the same as in our previous N N and Y N scattering calculations, the ∆K state with L = 0 and I = 1 is a weakly bound state with about 2 MeV binding energy, while the one with I = 2 is unbound in the present one-channel calculation.

We confirm our previous prediction of a d * state with I(J P ) = 0(3 + ) [Phys. Rev. C 60, 045203 (1999)] and report for the first time based on a microscopic calculation that d * has about 2/3 hidden color (CC) configurations and thus is a hexaquark-dominated exotic state. By performing a more elaborate dynamical coupled-channels investigation of the ∆∆-CC system within the framework of resonating group method (RGM) in a chiral quark model, we found that the d * state has a mass of about 2.38 − 2.42 GeV, a root-mean-square radius (RMS) of 0.76 − 0.88 fm, and a CC fraction of 66% − 68%. The last may cause a rather narrow width to d * which, together with the quantum numbers and our calculated mass, is consistent with the newly observed resonance-like structure (M ≈ 2380 MeV, Γ ≈ 70 MeV) in double-pionic fusion reactions reported by WASA-at-COSY Collaboration.PACS numbers: 14.20. Pt, 13.75.Cs, 12.39.Jh, 24.10.Eq The ABC effect has drawn physicists' great attention since its observation in 1961 in the pd reaction [1]. In recent years, much experimental progress in exploring the nature of the ABC effect has been made. In 2009, the CELSIUS/WASA Collaboration measured the most basic double-pionic fusion reaction pn → dπ 0 π 0 with an incident proton energy of 1.03 GeV and 1.35 GeV [2], and found significant enhancements in the ππ invariant mass spectrum at ππ invariant mass below 0.32 GeV 2 and also in the dπ invariant mass spectrum at ∆ resonance region. To accommodate these data as well as the energy dependence of the total cross section at √ s < 2.5 GeV, the conventional t-channel ∆∆ intermediate state is found to be not sufficient, and a new structure, namely an s-channel resonance with mass of about 2.36 GeV and width of about 80 MeV, is expected. In 2011, the WASA-at-COSY Collaboration further measured the pn → dπ 0 π 0 reaction with the beam energies of 1.0−1.4 GeV which cover the transition region of the conventional t-channel ∆∆ process [3]. They found that neither the t-channel ∆∆ process nor the Roper resonance process can explain the data, and an s-channel resonance with quantum numbers of I(J P ) = 0(3 + ), mass of about 2.37 GeV and width of about 70 MeV is indeed needed to describe the data. Recently, the WASA-at-COSY Collaboration measured the polarized np scattering through the quasi-free process dp → p spectator np [4,5]. By incorporating the newly measured A y data into the SAID analysis, they obtained a pole in the 3 D 3 -3 G 3 waves at (2380 ± 10)+ i(40 ±5) MeV, which again supports the existence of a resonance, called d * , as mentioned in Ref. [3]. Further evidence of this resonance has also been reported in the quasi-free np → npπ 0 π 0 reaction [6]. Since its mass is above the threshold of ∆N π channel, while its width is much smaller than the decay width of ∆, this resonance must be a very interesting state involving new physical mechanisms and it is obviously worthwhile investigating.Theoretically, the possibility of the existence of dibaryon states was first proposed in 1964 by Dyson a...

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The structure and decay properties of d * have been detailedly investigated in both the chiral SU(3) quark model and the extended chiral SU(3) quark model that describe the energies of baryon ground states and the nucleon-nucleon (NN) scattering data satisfactorily. By performing a dynamical coupled-channels study of the system of ΔΔ and hidden-color channel (CC) with quantum numbers I(J P ) = 0(3 + ) in the framework of the resonating group method (RGM), we find that the d * has a mass of about 2.38-2.42 GeV and a root-mean-square radius (RMS) of about 0.76-0.88 fm. The channel wave function is extracted by a projection of the RGM wave function onto the physical basis, and the fraction of CC component in the d * is found to be about 66%-68%, which indicates that the d * is a hexaquark-dominated exotic state. Based on this scenario the partial decay widths of d * → dπ 0 π 0 and d * → dπ + π − are further explicitly evaluated and the total width is then obtained by use of the branching ratios extracted from the measured cross sections of other possible decay channels. Both the mass and the decay width of d * calculated in this work are compatible with the data (M ≈ 2380 MeV, Γ ≈ 70 MeV) reported by WASA-at-COSY Collaboration. hexaquark state, d * (2380), quark model, hidden-color channel PACS number(s): 14.20.Pt, 13.75.Cs, 12.39.Jh, 13.30.Eg Citation: