相关论文: Structure of Pion Photoproduction Amplitudes
We compare the low-energy partial wave analyses $\pi N$ scattering with a high-energy data via finite energy sum rules. We construct a new set of amplitudes by matching the imaginary part from the low-energy analysis with the high-energy,…
The Fubini-Furlan-Rossetti sum rule for pion photoproduction on the nucleon is evaluated by dispersion relations at constant t, and the corrections to the sum rule due to the finite pion mass are calculated. Near threshold these corrections…
A Regge model with absorptive corrections is employed in a global analysis of the world data on positive and negative pion photoproduction for photon energies from 3 to 8 GeV. In this region resonance contributions are expected to be…
We present the results of an energy-dependent and set of single-energy partial-wave analyses of single-pion photoproduction data. These analyses extend from threshold to 2 GeV in the laboratory photon energy, and update our previous…
We present a Regge model for pion photoproduction which is basically free of parameters within the framework of the s-channel helicity amplitude. We use coupling constants of all exchanged mesons determined from empirical decay widths or…
We present a systematic analysis of backward pion photoproduction for the reactions gamma p -> pi0 p and gamma p -> pi+ n. Regge phenomenology is applied at invariant collision energies above 3 GeV in order to fix the reaction amplitude. A…
Results of the recently developed unitary isobar model (MAID) are presented for the spin asymmetries, structure functions and relevant sum rules in the resonance region. The model describes the presently available data for single-pion…
The questions on the presense and quantitative role of the constant terms in the real part of the high-energy photon-nucleon and photon-nucleus amplitudes representing the contribution of the non-Regge (the fixed j=0-pole) singularities in…
The relativistic amplitudes of pion photo- and electroproduction are calculated by dispersion relations at constant t. Several sum rules and low-energy theorems for the threshold amplitudes are investigated within this technique. The…
We consider multipole amplitudes for low-energy pion photoproduction, constructed with minimal model dependence, at single energies. Comparisons with fits to the full resonance region are made. Explanations are suggested for the…
The reaction $\gamma p \to \pi^0 p$ is investigated in the energy range above the resonance region. The amplitudes include the leading Regge singularities in the cross-channel and correctly describe the differential cross section for beam…
Two approaches for analysis of pion photo- and electroproduction on nucleons in the resonance energy region are checked at $Q^2=0$ using the results of GWU(VPI) partial-wave analysis of photoproduction data. The approaches are based on…
A partial-wave analysis of single-pion photoproduction data has been completed. This study extends from threshold to 2 GeV in the laboratory photon energy, focusing mainly on the influence of new measurements and model-dependence in the…
A Regge model with absorptive corrections is employed in a global analysis of the world data on the reactions gamma p -> pi0 p and gamma n -> pi0 n for photon energies from 3 to 18 GeV. In this region resonance contributions are expected to…
The relativistic amplitudes of pion photoproduction are evaluated by dispersion relations at t=const. The imaginary parts of the amplitudes are taken from the MAID model covering the absorption spectrum up to center-of-mass energies W = 2.2…
A family of exact sum rules for the one-polaron spectral function in the low-density limit is derived. An algorithm to calculate energy moments of arbitrary order of the spectral function is presented. Explicit expressions are given for the…
We review the status of a Fubini-Furlan-Rossetti sum rule for the photoproduction of pions from nucleons, indicating how well this sum rule is satisfied using a recent analysis of pion photoproduction data. Our results are discussed in…
The reaction ${\gamma}N \to {\eta}N$ is studied in the high-energy regime (with photon lab energies $E_{\gamma}^{\textrm{lab}} > 4$ GeV) using information from the resonance region through the use of finite-energy sum rules (FESR). We…
We investigate pion photoproduction off the proton in a manifestly gauge-invariant chiral unitary extension of chiral perturbation theory. In a first step, we consider meson-baryon scattering taking into account all next-to-leading order…
We extract constraints on the pion distribution amplitude from available data on the pion-photon transition form factor in the framework of light-cone sum rules. A pronounced discrepancy $(2.7-3)\sigma$ between the Gegenbauer expansion…