Study The P-wave Dπ Coupled Channel Scattering Using The Chiral Unitary Approach

The interaction between hadrons, the internal structure and the properties of hadrons are the main topics in the field of hadron physics. Quantum Chromodynamics (QCD) is the most successful theory describing strong interaction. However, due to the non-perturbative nature of QCD in the small momentum scale, one has to deal with the non-perturbative QCD effects in low energy region with the help of various effective models or approximate methods. As a low-energy effective field theory, chiral unitary approach (ChUA) has achieved great success in explaining the experimental data of meson-meson scattering in low energy.In recent years, many suspected exotic hadron states were observed experimentally. Among them, there were some charmed vector mesons with quantum number Jp=1-and some vector-like mesons with uncertain quantum numbers Jp such as D’(2007)0, D*(2010)±, D1(2420)±and D’(2640)±. These new heavy mesons have the same quantum numbers with the P-wave interactions between chiral Goldstone boson and the pseudo-scalar meson ground state, and they are very close to the threshold of corresponding channels. So, it is signification for understanding these heavy meson properties to study P-wave interactions between light pseudo-scalar mesons and heavy mesons.In this thesis, the ChUA is used to study P-Wave scatterings between the charmed pseudo-scalar meson and light pseudo-scalar meson, containing Dπ, Dη and DSK coupled channels. Starting from the ChPT lagrangian, the scattering amplitude V in the lowest order was calculated, and the full scattering amplitude was obtained by solving the coupling Bethe-Salpeter (BS) equation. By finding the poles of the total scattering amplitude in different Riemann sheets and comparing them with the experimental data, we can get some information about the resonance states generated dynamically.In this thesis, we dealt with the divergence of one loop integral with the3-momentum cut-off regularization method, the only free parameter in our calculation is the3-momentum cut-off qmax. We took the parameter as1.2GeV、1.5GeV and1.8GeV respectively, and investigated the qmax-dependence of the results. It was found that the parameter dependence is not strong. A charmed vector meson was found which is generated dynamically in the P-Wave scattering between the charmed pseudo-scalar meson and light pseudo-scalar meson, with Jp=1-, I=1/2, S=0and C=1. When qmax is taken as1.5GeV, the mass and width of this state are M=2132.8MeV and г=1.99MeV respectively. In the formalism of this work, this state is taken as a meson-meson molecular state. The charmed vector meson generated dynamically could not fit with those observed experimentally. So it indicated that the existed charmed vectors should not be molecular states.