The dynamical model of pion electroproduction developed in Physical Review C63, 055201 (2001) has been extended to investigate the weak pion production reactions. With the Conserved Vector Current(CVC) hypothesis, the weak vector currents are constructed from electromagnetic currents by isospin rotations. Guided by the effective chiral lagrangian method and using the unitary transformation method developed previously, the weak axial vector currents for π production are constructed with no adjustable parameters. In particular, the N-∆ transitions at Q 2 → 0 are calculated from the constituent quark model and their Q 2 -dependence is assumed to be identical to that determined in the study of pion electroproduction. The main feature of our approach is to renormalize these bare N-∆ form factors with the dynamical pion cloud effects originating from the non-resonant π production mechanisms. The predicted cross sections of neutrino-induced pion production reactions, N (ν µ , µ − π)N , are in good agreement with the existing data. We show that the renormalized(dressed) axial N-∆ form factor contains large dynamical pion cloud effects and this renormalization effects are crucial in getting agreement with the data. We conclude that the N-∆ transitions predicted by the constituent quark model are consistent with the existing neutrino induced pion production data in the ∆ region, contrary to the previous observations. This is consistent with our previous findings in the study of pion electroproduction reactions. However, more extensive and precise data of neutrino induced pion production reactions are needed to further test our model and to pin down the Q 2 -dependence of the axial vector N-∆ transition form factor.

η meson production in both proton-proton and proton-neutron collisions is investigated within a relativistic meson exchange model of hadronic interactions. It is found that the available cross section data can be described equally well by either the vector or pseudoscalar meson exchange mechanism for exciting the S 11 (1535) resonance. It is shown that the analyzing power data can potentially be very useful in distinguishing these two scenarios for the excitaion of the S 11 (1535) resonance.

We show that two almost degenerate poles near the piDelta threshold and the next higher mass pole in the P11 partial wave of piN scattering evolve from a single bare state through its coupling with piN, etaN, and pipiN reaction channels. This finding provides new information on understanding the dynamical origins of the Roper N{*}(1440) and N{*}(1710) resonances listed by Particle Data Group. Our results for the resonance poles in other piN partial waves are also presented.

We develop a dynamical coupled-channels model of K − p reactions, aiming at extracting the parameters associated with hyperon resonances and providing the elementary antikaon-nucleon scattering amplitudes that can be used for investigating various phenomena in the strangeness sector such as the production of hypernuclei from kaon-nucleus reactions. The model consists of (a) meson-baryon (M B) potentials v M ′ B ′ ,M B derived from the phenomenological SU(3) Lagrangian, and (b) vertex interactions Γ M B,Y * for describing the decays of the bare excited hyperon states (Y * ) into M B states. The model is defined in a channel space spanned by the two-bodyKN , πΣ, πΛ, ηΛ, and KΞ states and also the three-body ππΛ and πKN states that have the resonant πΣ * andK * N components, respectively. The resulting coupled-channels scattering equations satisfy the multichannel unitarity conditions and account for the dynamical effects arising from the offshell rescattering processes. The model parameters are determined by fitting the available data of the unpolarized and polarized observables of the K − p →KN, πΣ, πΛ, ηΛ, KΞ reactions in the energy region from the threshold to invariant mass W = 2.1 GeV. Two models with equally good χ 2 fits to the data have been constructed. The partial-wave amplitudes obtained from the constructed models are compared with the results from a recent partial-wave analysis by the Kent State University group. We discuss the differences between these three analysis results. Our results at energies near the threshold suggest that the higher partial waves should be treated on the same footing as the S wave if one wants to understand the nature of Λ(1405)1/2 − using the data below theKN threshold, as will be provided by the J-PARC E31 experiment.