Related papers: Roper Electroproduction Amplitudes in a Chiral Con…
Pion electroproduction amplitudes predicted by three theoretical models in the $Q^2 \leq 0.5$ (GeV/c)$^2$ region are compared. The objective is to facilitate the analyses of the data from new experiments on investigating the pion cloud…
We calculate the electric quadrupole to magnetic dipole transition ratio $E2/M1$ for the reaction $\gamma N \ra \Delta(1232)$ in the chiral quark soliton model. The calculated $E2/M1$ ratio is in a good agreement with the very new…
Using a chiral constituent quark approach based on the broken SU(6) \otimes O(3) symmetry, we focus on the spectroscopy of isospin-1/2 nucleonic resonances. A model for the eta photoproduction, embodying all known nucleonic resonances,…
We present an amplitude analysis of high-energy polarized photoproduction of $\pi^-\Delta^{++}$ within a Regge exchange framework. A Regge amplitude model incorporating $\pi$, $\rho$, $b_1$, and $a_2$ trajectory exchanges is fit…
Helicity amplitudes for the $\gamma^* N \to \Delta$ transition are calculated using the cloudy bag model. A correction for center-of-mass motion is carried out using a modified Peierls-Thouless projection method. This reduces the magnitude…
The spectrum of $\bar q q$ mesons in a model where the only interaction is a linear Coulomb-like instantaneous confining potential is studied. The single-quark Green function as well as the dynamical chiral symmetry breaking are obtained…
Results on elastic electroproduction of rho mesons are presented for a photon virtuality in the range 1 < Q^2 < 60 GeV^2 and for a hadronic centre of mass energy in the range 30 < W < 140 GeV. The shape of the (pi pi) mass distribution is…
We calculate the width of the Roper resonance at next-to-leading order in a systematic expansion of baryon chiral perturbation theory with pions, nucleons, and the delta and Roper resonances as dynamical degrees of freedom. Three unknown…
We examine the role of the elementary isoscalar pion--nucleon scattering amplitude in the description of the processes $pp \to pp\pi^0$ and $pp\to d\pi^+$ at threshold. We argue that the presently used tree level dimension two approximation…
We compute the amplitudes for the electromagnetic $\gamma_v N \to \Delta$ transition in the framework of soliton models with quarks and mesons. The ratios E2/M1 and C2/M1 as functions of the photon four-momentum squared are dominated by the…
We review the development of the most general analytic form of the cross section, dependent upon the three polarization vectors of the beam, target and recoil baryon, including all single, double and triple-polarization terms involving 16…
Due to multiple possible polarizations hard exclusive production of tensor mesons by virtual photons or in heavy meson decays offers interesting possibilities to study the helicity structure of the underlying short-distance process.…
A new analysis of S-wave production amplitudes for the reaction $\pi^- p_{\uparrow} \rightarrow \pi^+ \pi^- n$ on a transversely polarized target is performed. It is based on the results obtained by the CERN-Cracow -Munich collaboration in…
We study whether the nonmonotonic behavior found in the differential cross section of the phi-meson photoproduction near threshold can be described by a resonance. The resonant contribution is evaluated by using an effective Lagrangian…
We present a simple nonlinear resonant analog circuit which demonstrates quantization of resonating amplitudes, for a given excitation level. The system is a simple RLC resonator where C is an active capacitor whose value is related to the…
We study pseudoscalar and scalar mesons using a practical and symmetry preserving truncation of QCD's Dyson-Schwinger equations. We investigate and compare properties of ground and radially excited meson states. In addition to exact results…
A fast restoration of chiral symmetry in excited mesons is demonstrated. A minimal "realistic" chirally symmetric confining model is used, where the only interaction between quarks is the linear instantaneous Lorentz-vector confining…
A Dyson-Schwinger-based model of pomeron exchange is employed to calculate diffractive rho-, phi- and J/psi-meson electroproduction cross sections. It is shown that the magnitude of the current-quark mass m_f of the quark and antiquark…
The photo- and electroproduction of eta, eta-prime mesons on nucleons are investigated within a relativistic chiral unitary approach based on coupled channels. The s-wave potentials for electroproduction and meson-baryon scattering are…
The photo-production of nucleon resonances is calculated based on a chiral constituent quark model including both relativistic corrections H{rel} and two-body exchange currents, and it is shown that these effects play an important role. We…