Related papers: Recent progress in pion photo- and electroproducti…
The $\sigma$-exchange and $f_2$-exchange mechanisms for $\rho$ meson photoproduction are re-examined. Then the commonly employed $\sigma$-exchange amplitude is revised by using the recent information from the analyses on the $\rho \to…
The photon pair production by pion annihilation in a hot and dense medium at the chiral phase transition is investigated within a chiral quark model. As a direct consequence of this transition the $\sigma$ meson appears as a bound state in…
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…
With an effective Lagrangian approach, we analyze several NN \to NN\pi\pi channels by including various resonances with mass up to 1.72 GeV. For the channels with the pion pair of isospin zero, we confirm the dominance of N*(1440)\to…
The unitary isobar model MAID is used for a partial wave analysis of pion photoproduction and electroproduction data on the nucleon. In particular we have taken emphasis on the region of the Delta(1232) resonance and have separated the…
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. Namely, we add a resonance to a model consisting of Pomeron and (pi,eta)…
Photo- and electroproduction of $K\Sigma$ have been investigated near their production thresholds by using an effective Lagrangian approach. For this purpose, the background amplitude is constructed from suitable Feynman diagrams, whereas…
QCD-based scaling arguments predict the predominance of longitudinal over transverse electroproduction of pions by terms $\propto Q^2$. However, data from JLAB, Cornell and DESY, covering a wide kinematical range $1 < Q^2 < 11\, {\rm…
We analyze the new threshold data for neutral pion photoproduction off protons in the framework of heavy baryon chiral perturbation theory. We show that large loop corrections are needed to understand the S--wave multipole $E_{0+}$ and that…
Neutrino-induced pion and photon production from nucleons and nuclei are important for the interpretation of neutrino-oscillation experiments, and these processes are potential backgrounds in the MiniBooNE experiment [A. A. Aquilar-Arevalo…
We consider pion electroproduction on a proton target close to threshold for Q^2 in the region 1-10 GeV^2. The momentum transfer dependence of the S-wave multipoles at threshold, E_{0+} and L_{0+}, is calculated using light-cone sum rules.
Pion electroproduction off the proton is analyzed in a new framework based on a general parametrization of transition amplitudes, including constraints from gauge invariance and threshold behavior. Data with energies $1.13~{\rm…
In this work, the $\eta^\prime$ meson photoproduction near threshold is studied in the quark model framework. A pseudovector effective Lagrangian is introduced for the $\eta^\prime NN$ coupling and the newly published data from the SAPHIR…
We study the photo- and electro-productions of the vector kaon off the proton, i.e., $\gamma^{(*)}p\to K^{*+}\pi^0\Sigma^0$, and investigate the line shape of the $\pi^0\Sigma^0$ invariant mass in an effective Lagrangian approach with the…
We report on two pion-photoproduction measurements in the threshold region conducted in the A2 collaboration at MAMI with the almost 4{\pi} Crystal Ball detector. The first was with a linearly polarized photon beam and unpolarized…
Within a dynamical coupled-channels model which has already been fixed from analyzing the data of the pi N -> pi N and gamma N -> pi N reactions, we present the predicted double pion photoproduction cross sections up to the second resonance…
We consider the reaction g+d -> pi+d in a wide energy range around and above the eta-meson photoproduction threshold at backward CM angles of the outgoing pion. Our theoretical analysis is essentially motivated by the recent measurements of…
In these proceedings we present preliminary $\pi^{+}\pi^{-}$ electroproduction cross sections off protons in the kinematical area of 1.4 GeV $< W <$ 1.8 GeV and 0.4 GeV$^{2}$ $< Q^{2} < 1.1$ GeV$^{2}$. Our results extend the kinematical…
Pion photoproduction off the nucleon close to threshold is studied in covariant baryon chiral perturbation theory at O($p^3$) in the extended-on-mass-shell scheme, with the explicit inclusion of the $\Delta(1232)$ resonance using the…
We investigate the charged pion photoproduction off the proton target with the Delta(1232) baryon in the final state, i.e. gamma p -> pi^- Delta^++(1232) and gamma p -> pi^+ Delta^0(1232), based on the effective Lagrangian method, beyond…