Related papers: New Narrow Nucleon N*(1685)
The gamma n -> K+ K- n reaction on 12C has been studied by measuring both K+ and K- at forward angles. A sharp baryon resonance peak was observed at 1.54 +- 0.01 GeV with a width smaller than 25 MeV and a Gaussian significance of 4.6 sigma.…
The isobar models eta-MAID and eta'-MAID have been used to analyze new data on quasi-free eta photoproduction on the deuteron from Bonn and recent eta' data on the proton from Jlab. In eta photoproduction on the neutron a bump around W=1700…
New results on quasi-free $\eta$ photoproduction on the neutron and proton bound in a deuteron target are presented. The $\gamma n \to \eta n$ quasi-free cross section reveals a bump-like structure which is not seen in the cross section on…
A combined analysis of photoproduction data on \gamma p to \pi N, eta N was performed including the data on K Lambda and K Sigma. The data are interpreted in an isobar model with s--channel baryon resonances and pi, rho,(omega), K, and K^*…
A narrow baryon resonance is observed in invariant mass of the pKshort system formed in neutrino and antineutrino collisions with nuclei. The mass of the resonance is estimated as (1533+-5)MeV. The observed width is less than 20 MeV, and is…
Several recent experiments have reported evidence for a narrow baryon resonance with positive strangeness ($\Theta^+$) at a mass of 1.54 GeV/$c^2$. Baryons with $S=+1$ cannot be conventional $qqq$ states and the reports have thus generated…
The newest progress on the study of the strangeness in the proton and in the lowest negative parity nucleon excited state $N^*(1535)$ is reviewed. Implications on the internal quark structure of the proton, $N^*(1535)$ and other baryons are…
An existing single resonance model with S11, P11 and P13 Breit-Wiegner resonances in the s-channel has been re-applied to the old pi N --> K Lambda data. It has been shown that the standard set of resonant parameters fails to reproduce the…
Results of a partial wave analysis of new high-statistics data on $\gamma p\to p\eta$ from MAMI are presented. A fit using known broad resonances and only standard background amplitudes can not describe the relatively narrow peaking…
Low-energy eta photoproduction on the nucleon is studied in an effective Lagrangian approach that contains Born terms, vector meson and nucleon resonance contributions. The resonance sector includes the $S_{11}(1535)$, $P_{11}(1440)$ and…
We develop a reaction model for $\eta$ photoproduction off the deuteron ($\gamma d\to\eta pn$), and study the reaction at a special kinematics, where the photon beam energy is $\sim 0.94$ GeV and the scattered proton is detected at $\sim…
The newly discovered exotic $\Theta$ baryon of mass 1540 MeV (and very small width) truly has a very low mass, if it is a pentaquark system of even parity. A schematic model in which the coherent interaction of $u\bar s$ and $d\bar s$ pairs…
The helicity-dependent observable $E$ for the reaction $\gamma d\to \eta n (p)$ with a spectator proton was recently measured by the A2 Collaboration at MAMI in Mainz. The data were interpreted as further evidence for a narrow resonance…
The existence of an anti-decuplet of pentaquark particles has been predicted some year ago within the chiral soliton model. In the last year, several experimental groups have reported evidence for a S=+1 baryon resonance, with mass ranging…
We review recent progress in our understanding of the nucleon excitation spectrum. Thanks to dedicated efforts at facilities such as ELSA, MAMI and Jefferson Lab, several new nucleon resonances have been discovered, and evidence for…
Motivated by the recent discovery of the exotic S=+1 narrow baryon resonance Theta^+ at 1540 MeV, with quark content {uudd sbar}, we conjecture the existence of its anti-charmed analogue Theta_c, with quark content {uudd cbar}, and compute…
The existence of non-strange partner of pentaquark, the J^p = 1/2^+ narrow resonance, has been investigated by utilizing kaon photoproduction off a proton. It is found that the corresponding mass is 1650 MeV and the appropriate observables…
We study $\eta$ photoproduction off the deuteron ($\gamma d\to\eta pn$) at a special kinematics: $\sim 0.94$ GeV of the photon beam energy and $\sim 0^\circ$ of the scattering angle of the proton. This kinematics is ideal to extract the…
The nucleon resonances near 2 GeV are investigated through the $\Sigma$(1385) and $\Lambda(1520)$ photoproductions within a Regge-plus-resonance approach based on the new experimental data released by the CLAS Collaboration. The…
Different interpretations of narrow structures at $W\sim 1.68$ and $W\sim 1.72$ GeV observed in several reactions are discussed. It is questionable whether interference phenomena could explain the whole complex of experimental findings.…