Related papers: Roper Electroproduction Amplitudes in a Chiral Con…
We compute nucleon and Roper e.m. elastic and transition form factors using a symmetry-preserving treatment of a contact-interaction. Obtained thereby, the e.m. interactions of baryons are typically described by hard form factors. In…
First radial excitations of the scalar meson nonet and pseudoscalar mesons \eta, \eta' are described in a nonlocal chiral quark model of the Nambu--Jona-Lasinio type with 't Hooft interaction. In this model simple form factors are used,…
The production of mesons in nucleon-nucleon collisions is reviewed from the viewpoint of the meson-exchange picture. In the first part various possible production mechanisms and their relative importance are discussed. In addition, general…
We express the leading electromagnetic corrections in K-> pi pi amplitudes as integrals over the virtual photon squared-momentum Q^2. The high Q^2 behavior is obtained via the operator product expansion. The low Q^2 behavior is calculated…
We investigate the longitudinal and transverse polarized cross-sections of the leptoproduction of the rho meson in the high energy limit. Our model is based on the computation of the impact factor gamma*(lambda_gamma) -> rho(lambda_rho)…
Selected recent results from the H1 and ZEUS experiments are reviewed, illustrating some of the many facets of ``meson physics'' at the HERA ep collider. The results cover exclusive elastic and proton-dissociative diffractive vector meson…
We estimate the leading order amplitudes for exclusive photon and meson electroproduction reactions at large Q^2 in the valence region in terms of skewed quark distributions. As experimental investigations can currently only be envisaged at…
We explore the role of a scalar meson exchange interaction between quarks in a semirelativistic constituent quark model where the quarks are also subject to a linear confinement. We search for a variational solution and study how the…
We present an improved study of the electromagnetic form factors of the nucleon and of the Roper-nucleon transition using an extended version of the effective action of soft-wall AdS/QCD. We include novel contribution from additional…
We present an overview of the correlation-matrix methods developed recently by the CSSM Lattice Collaboration for the isolation of excited states of the nucleon. Of particular interest is the first positive-parity excited-state of the…
We measured angular distributions of differential cross section, beam analyzing power, and recoil polarization for neutral pion electroproduction at Q^2 = 1.0 (GeV/c)^2 in 10 bins of W across the Delta resonance. A total of 16 independent…
We consider pion electroproduction close to threshold for $Q^2$ in the region 1-10 GeV$^2$ on a nucleon target. The momentum transfer dependence of the S-wave multipoles at threshold, $E_{0+}$ and $L_{0+}$, is calculated in the chiral limit…
We study electromagnetic properties of the nucleon and Roper resonance in a chiral quark-diquark model including two kinds of diquarks needed to describe the nucleon: scalar and axial-vector diquarks. The nucleon and Roper resonance are…
A simple model of a composite nucleon is developed in which a fermion and a boson, representing quark and diquark constituents of the nucleon, form a bound state owing to a contact interaction. Photon and pion couplings to the quark provide…
Transition helicity amplitudes $\gamma_{v}NN^*$ (electrocouplings) were determined for prominent excited proton states with masses below 1.8 GeV in independent analyses of major meson electroproduction channels: $\pi^{+}n$, $\pi^0p$ and…
We discuss the electroproduction of pseudoscalar ($0^{-+}$) or scalar ($0^{++}$) meson production off the scalar target. The most general formulation of the differential cross section for the $0^{-+}$ or $0^{++}$ meson production process…
The amplitudes for photoproduction of two pseudoscalars on a nucleon are expanded in the overall c.m. frame in a model independent way with respect to the contribution of the final state partial wave of total angular momentum $J$ and its…
Exclusive pi0 electroproduction from nucleons can be related to transversity, the tensor charge, and other quantities related to transversity. This process isolates C-parity odd and chiral odd combinations of t-channel exchange quantum…
We report on the determination of the electrocouplings for the transition from the proton to the $N(1675){\frac{5}{2}}^-$ resonance state using recent differential cross section data on $e p \rightarrow e\pi^+ n$ by the CLAS collaboration…
We study in perturbative QCD the helicity ampltiudes of the process $\gamma^{*} p \to \rho p $ at large virtualities $Q$ of the photon $\gamma^{*}$. We estimate all spin flip amplitudes taking into account an important effect of the scale…