相关论文: Is there a narrow $N(1685)$?
New data on the polarization observables T, P, and H for the reaction $\gamma p \to p\pi^0$ are reported. The results are extracted from azimuthal asymmetries when a transversely polarized butanol target and a linearly polarized photon beam…
A combined analysis of new eta photoproduction data for total and differential cross sections, target asymmetry and photon asymmetry is presented. Using a few reasonable assumptions we perform the first model-independent analysis of the…
Single nucleon knockout reactions must be described in a consistent framework in order to extract information about nuclear structure and reaction mechanisms. Consistent relativistic models for the direct knockout contribution to the (e,…
We collected notes and simple estimates about putative narrow nucleon N*(1685) - the candidate for the non-strange member of the exotic anti-decuplet of baryons. In particular, we consider the recent high precision data on eta…
The double-polarization observable $E$ and helicity-dependent cross sections $\sigma_{1/2}$, $\sigma_{3/2}$ have been measured for the photoproduction of $\pi^0$ pairs off quasi-free protons and neutrons at the Mainz MAMI accelerator with…
A phenomenological analysis of radiative $V\to P\gamma$ and $P\to V\gamma$ decays is performed in order to determine the gluonic content of the $\eta^\prime$ wave function. Our result shows that there is no evidence for such a gluonium…
We analyze the existing data on the angular distributions of the $\gamma\gamma\to \pi^+ \pi^- ,\pi^0 \pi^0$ reactions with using of the unitary model for helicity 2 amplitude. The purpose is to obtain the D--wave parameters and S--wave…
This work presents a simple method to determine the significant partial wave contributions to experimentally determined observables in pseudoscalar meson photoproduction. First, fits to angular distributions are presented and the maximum…
A phenomenological analysis of radiative $V\to P\gamma$ and $P\to V\gamma$ decays is performed with the purpose of determining the gluonic content of the $\eta$ and $\eta^\prime$ wave functions. Our results show that within our model there…
We have examined the existence of the $N^*(1685)$ resonance, which is recently listed by the Particle Data Group as a one-star nucleon resonance, by using a covariant isobar model for kaon photoproduction and assuming that the resonance has…
The reactions pp\to d\pi^+\eta and pn\to d\pi^0\eta are of special interest for investigating the a_0(980) (J^P=0^+) resonance in the process NN \to da_0 \to d\pi\eta. We study some aspects of those reactions within a general formalism and…
Recent data on photoproduction of $\eta'$ mesons off protons have been included in the data base for the Bonn-Gatchina partial wave analysis. The real and imaginary parts of the $S$-wave $\eta^\prime p\to \eta^\prime p$ scattering amplitude…
The N*(1535) resonance contributions to the pn->d\phi reaction are evaluated in an effective Lagrangian model. The \pi-, \eta-, and \rho-meson exchange are considered. It is shown that the contributions from \pi- and \rho-meson exchange are…
The production of eta' mesons in photon- and hadron-induced reactions has been revisited in view of the recent additions of high-precision data to the world data base. Based on an effective Lagrangian approach, we have performed a combined…
The reaction $\gamma p\to p\pi^0\eta$ has been studied with the CBELSA detector at the tagged photon beam of the Bonn electron stretcher facility. The reaction shows contributions from $\Delta^+(1232)\eta$, $N(1535)^+\pi^0$ and $pa_0(980)$…
In the search for missing baryonic resonances, many analyses include data from a variety of pion- and photon-induced reactions. For elastic $\pi N$ scattering, however, usually the partial waves of the SAID or other groups are fitted,…
Amplitudes for the reaction $\pi^-p\to \Lambda K^0$ are reconstructed from data on the differential cross section $d\sigma/d\Omega$, the recoil polarization $P$, and on the spin rotation parameter $\beta$. At low energies, no data on…
The nucleon-like member $N(1685)$ of the speculative baryon antidecuplet denotes one possible explanation for the narrow peak-structure around $W = 1.68$ GeV observed in the total cross section of $\eta$-photoproduction off the neutron. If…
A chiral quark-model approach is adopted to study the $\gamma p\rightarrow \eta'p$ and $\gamma n\rightarrow \eta' n$. Good descriptions of the recent observations from CLAS and CBELSA/TAPS are obtained. Both of the processes are governed by…
Within a chiral constituent quark model approach, $\eta$-meson production on the proton {\it via} electromagnetic and hadron probes are studied. With few parameters, differential cross-section and polarized beam asymmetry for \gamma p \to…