相关论文: A model for the Delta(1600) resonance and gamma N …

Starting with a spectator quark model developed for the nucleon (N) and the Delta in the physical pion mass region, we extend the predictions of the reaction gamma N -> Delta to the lattice QCD regime. The quark model includes S and D waves…

The $\Delta(1232) \to \gamma^\ast N$ magnetic dipole form factor ($G_M^\ast$) is described here within a new covariant model that combines the valence quark core together with the pion cloud contributions. The pion cloud term is…

We consider here a manifestly covariant quark model of the nucleon and the Delta, where one quark is off-shell and the other two quarks form an on-shell diquark pair. Using this model, we have shown previously that the nucleon form factors…

We report on ongoing work to determine the pion-cloud contribution to the electromagnetic $N\rightarrow\Delta$ transition form factors. The starting point is an $SU(6)$ spin-flavor symmetric constituent-quark model with instantaneous…

We examine the contribution of the pion cloud to the electromagnetic $N \rightarrow \Delta$ transition form factors within a relativistic hybrid constituent-quark model. In this model baryons consist not only of the $3q$ valence component,…

We study the N-Delta-gamma transition in the Dyson-Schwinger approach. The nucleon and Delta baryons are treated as quark-diquark bound states, where the ingredients of the electromagnetic transition current are computed self-consistently…

The magnetic-dipole form factor and the ratios R_EM and R_SM for the gamma* N -> Delta(1232)3/2}+ transition are predicted within light-front relativistic quark model up to photon virtuality Q2=12 GeV2. We also predict the helicity…

We study the $\gamma^\ast \Lambda \to \Sigma^0$ transition form factors by applying the covariant spectator quark model. Using the parametrization for the baryon core wave functions as well as for the pion cloud dressing obtained in a…

We discuss the results of the covariant spectator quark model for the several $\gamma^\ast N \to N^\ast$ transitions, where $N$ is the nucleon and $N^\ast$ a nucleon excitation. More specifically, we present predictions for the form factors…

We apply the perturbative chiral quark model to the gamma N -> Delta transition. The four momentum dependence of the respective transverse helicity amplitudes A(1/2) and A(3/2) is determined at one loop in the pseudoscalar Goldstone boson…

A covariant spectator quark model is applied to estimate the valence quark contributions to the$ F1*(Q2) and F2*(Q2) transition form factors for the gamma N -> P11(1440) reaction. The Roper resonance, P11(1440), is assumed to be the first…

Radiative transitions gamma + Delta(1232) -> N^* are discussed in the nonrelativistic quark model with spin-orbit corrections for the 70-plet L^P=1^- nucleon resonances N^*. The reaction gamma + N -> gamma + Delta is considered as a tool to…

In this work, the electromagnetic and gravitational form factors of $\Delta$ isobars, as well as the electromagnetic $N-\Delta$ transition form factors are studied systematically and continuously using a covariant quark-diquark approach…

A constituent quark model based on the spectator formalism is applied to the gamma N -> N* transition for the three cases, where N* is the nucleon, the Delta and the Roper resonance. The model is covariant, and therefore can be used for the…

A model for the gamma p ----> pion+ pion- p reaction developed earlier is extended to account for all isospin channels. The model includes N, Delta(1232), N^*(1440) and N^*(1520) as intermediate baryonic states and the rho-meson as an…

The \gamma* N -> \Delta(1232) transition is a window on hadron shape deformation, the applicability of perturbative QCD at moderate momentum transfers, and the influence of nonperturbative phenomena on hadronic observables. We explain that…

Using a covariant spectator quark model we estimate valence quark contributions to the F1*(Q2) and F2*(Q2) transition form factors for the gamma N -> P11(1440) reaction. The Roper resonance, P11(1440), is assumed to be the first radial…

Electroproduction form factors describing the $\gamma^\ast p \to \Delta^+(1232), \Delta^+(1600)$ transitions are computed using a fully-dynamical diquark-quark approximation to the Poincar\'e-covariant three-body bound-state problem in…

A chiral quark-model approach is adopted to study the $\gamma p\rightarrow \pi^0p$ and $\gamma n\rightarrow \pi^0 n$ reactions. Good descriptions of the total and differential cross sections and single-polarization observables are obtained…

The form factors of $\gamma^* N \rightarrow \Delta(1600)$ transition is calculated within the light-cone sum rules assuming that $\Delta^+(1600)$ is the first radial excitation of $\Delta(1232)$. The $Q^2$ dependence of the magnetic dipole…