18 research outputs found
Photoproduction of Lambda(1405) and Sigma^{0}(1385) on the proton at E_\gamma = 1.5-2.4 GeV
Differential cross sections for and reactions have been measured in the photon energy range
from 1.5 to 2.4 GeV and the angular range of for the
scattering angle in the center-of-mass system. This data is the first
measurement of the photoproduction cross section. The
lineshapes of \LamS measured in and decay modes
were different with each other, indicating a strong interference of the isospin
0 and 1 terms of the scattering amplitudes. The ratios of \LamS
production to \SigS production were measured in two photon energy ranges: near
the production threshold ( GeV) and far from it ( GeV). The observed ratio decreased in the higher photon energy
region, which may suggest different production mechanisms and internal
structures for these hyperon resonances
Near-threshold Lambda(1520) production by the gamma p -> K+Lambda(1520) reaction at forward K+ angles
Differential cross sections and photon-beam asymmetries for the gamma p -> K+
Lambda(1520) reaction have been measured with linearly polarized photon beams
at energies from the threshold to 2.4 GeV at 0.6<cos(theta)<1. A new bump
structure was found at W=2.11 GeV in the cross sections. The bump is not well
reproduced by theoretical calculations introducing a nucleon resonance with
J<=3/2. This result suggests that the bump might be produced by a nucleon
resonance possibly with J>=5/2 or by a new reaction process, for example an
interference effect with the phi photoproduction having a similar bump
structure in the cross sections.Comment: 5 pages, 4 figures, published in Phys. Rev. Let
Measurement of the Reaction at Backward Angles
Cross sections for the have been measured at
backward angles using linearly polarized photons in the range 1.50 to 2.37 GeV.
In addition, the beam asymmetry for this reaction has been measured for the
first time at backward angles. The was detected at forward angles in
the LEPS spectrometer via its decay to and the K^+ was inferred using
the technique of missing mass. These measurements, corresponding to kaons at
far backward angles in the center-of-mass frame, complement similar CLAS data
at other angles. Comparison with theoretical models shows that the reactions in
these kinematics provide further opportunities to investigate the reaction
mechanisms of hadron dynamics.Comment: 6 figures, submitted to PRC rapid communication
Differential cross section and photon beam asymmetry for the gamma n -> K+ Sigma- reaction at Egamma=1.5-2.4 GeV
Differential cross sections and photon beam asymmetries have been measured
for the gamma n -> K+ Sigma- and gamma p -> K+ Sigma0 reactions separately
using liquid deuterium and hydrogen targets with incident linearly polarized
photon beams of Egamma=1.5-2.4 GeV at 0.6<cosTheta<1. The cross section ratio
of sigma(K+Sigma-)/sigma(K+Sigma0), expected to be 2 on the basis of the
isospin 1/2 exchange, is found to be close to 1. For the K+Sigma- reaction,
large positive asymmetries are observed indicating the dominance of the
K*-exchange. A large difference between the asymmetries for the K+Sigma- and
K+Sigma0 reactions can not be explained by simple theoretical considerations.Comment: 5 pages, 3 figures, accepted by Phys. Rev. Let
Backward-angle photoproduction of eta meson from protons at E_gamma = 1.6 - 2.4 GeV
Differential cross sections for eta photoproduction off protons have been
measured at E_gamma = 1.6 - 2.4 GeV in the backward direction. A bump structure
has been observed above 2.0 GeV in the total energy. No such bump is observed
in cross sections for eta', omega and pi0 photoproductions. It is inferred that
this unique structure in eta photoproduction is due to a baryon resonance with
a large portion of ss-bar strongly coupled to the etaN channel.Comment: 3 figures, Submitted to PR
Search for bound state via reaction at GeV
A search for bound state (the lightest kaonic nucleus) has been
performed using the reaction at
E=1.5-2.4 GeV at LEPS/SPring-8. The differential cross section of photo-production off deuterium has been measured for the first time in
this energy region, and a bump structure was searched for in the inclusive
missing mass spectrum. A statistically significant bump structure was not
observed in the region from 2.22 to 2.36 GeV/, and the upper limits of the
differential cross section for the bound state production were
determined to be 0.10.7 b (95 confidence level) for a set of
assumed binding energy and width values
Diffractive -meson photoproduction on proton near threshold
Photoproduction of -meson on protons was studied by means of linearly
polarized photons at forward angles in the low-energy region from threshold to
= 2.37 GeV. The differential cross sections at do
not increase smoothly as increases, but show a local maximum at
around 2.0 GeV. The angular distributions demonstrate that -mesons are
photo-produced predominantly by helicity-conserving processes, and the local
maximum is not likely due to unnatural-parity processes.Comment: 6 pages, error on the cross sections were corrected, accepted for
publication in Phys. Rev. Let