3,199 research outputs found
Baryon resonances and polarization transfer in hyperon photoproduction
A partial wave analysis is presented of data on photoproduction of hyperons
including single and double polarization observables. The large spin transfer
probability reported by the CLAS collaboration can be successfully described
with an isobar partial wave analysis.Comment: 12 pages, 9 figure
On photoexcitation of baryon antidecuplet
We show that the photoexcitation of the baryon antidecuplet, suggested by the
soliton classification of low-lying baryons, is strongly suppressed on the
proton target. The process occurs mostly on the neutron target. This
qualitative prediction can be useful in identifying the non-exotic members of
the antidecuplet in the known baryon spectrum. We also analyze the
interrelation between photocouplings of various baryon multiplets in the
soliton picture and in the nonrelativistic quark model.Comment: 9 pages, one Latex figur
Partial decay widths of baryons in the spin-momentum operator expansion method
The cross sections for photo- and pion-induced production of baryon
resonances and their partial decay widths to the two--body and multi--body
final states are calculated in the framework of the operator expansion method.
The approach is fully relativistic invariant, and it allows us to perform
combined analyses of different reactions imposing directly the analyticity and
unitarity constraints. All formulae are given explicitly in the form used by
the Crystal Barrel collaboration in the partial wave analysis.Comment: 15 pages, 6 figure
New Narrow Nucleon N*(1685)
We argue that the existence of a new narrow (Gamma < 25 MeV) nucleon
resonance N*(1685) is strongly supported by recent data on eta photoproduction
off the nucleon. The resonance has much stronger photo-coupling to the neutron
than to the proton. This nucleon resonance is a good candidate for the
non-strange member of the exotic anti-decouplet of baryons -- the partner of
the pentaquark Theta+. All up to date known properties of new N*(1685) are
summarized.Comment: Typos are corrected. Version published in JETP Letters (Pis'ma v
ZhETF
Lowering the Light Speed Isotropy Limit: European Synchrotron Radiation Facility Measurements
The measurement of the Compton edge of the scattered electrons in GRAAL
facility in European Synchrotron Radiation Facility (ESRF) in Grenoble with
respect to the Cosmic Microwave Background dipole reveals up to 10 sigma
variations larger than the statistical errors. We now show that the variations
are not due to the frequency variations of the accelerator. The nature of
Compton edge variations remains unclear, thus outlining the imperative of
dedicated studies of light speed anisotropy
Eta photoproduction on the neutron at GRAAL: Measurement of the differential cross section
In this contribution, we will present our first preliminary measurement of
the differential cross section for the reaction gamma+n->eta+n. Comparison of
the reactions gamma+p->eta+p for free and bound proton (D2 target) will also be
discussed.Comment: 6 pages, 4 figures, Proceedings of the 10th International Symposium
on Meson-Nucleon Physics and the Structure of the Nucleon, August
29-September 4 2004, Beijing, Chin
Eta photoproduction off the neutron at GRAAL: Evidence for a resonant structure at W=1.67 GeV
New (preliminary) data on eta photoproduction off the neutron are presented.
These data reveal a resonant structure at W=1.67 GeV.Comment: 8 pages, 4 figures. Published in Proceedings of Workshop on the
Physics of Excited Nucleons NSTAR2004, Grenoble, France, March 24 - 27,
pg.19
Eta photoproduction off the neutron at GRAAL
The gamma n -> eta n quasi-free cross section reveals a resonant structure at
W ~ 1.675 GeV. This structure may be a manifestation of a baryon resonance. A
priori its properties, the possibly narrow width and the strong photocoupling
to the neutron, look surprising. This structure may also signal the existence
of a narrow state.Comment: To appear in Proceedings of Workshop on the Physics of Excited
Nucleons NSTAR2005, 12 - 15 October 2005, Tallahassee, Florida, US
Measurement of eta photoproduction on the proton from threshold to 1500 MeV
Beam asymmetry and differential cross section for the reaction gamma+p->eta+p
were measured from production threshold to 1500 MeV photon laboratory energy.
The two dominant neutral decay modes of the eta meson, eta->2g and eta->3pi0,
were analyzed. The full set of measurements is in good agreement with
previously published results. Our data were compared with three models. They
all fit satisfactorily the results but their respective resonance contributions
are quite different. The possible photoexcitation of a narrow state N(1670) was
investigated and no evidence was found.Comment: 18 pages, 14 figures, 4 tables Submitted to EPJ
Precise Measurement of Sigma Beam Asymmetry for Positive Pion Photoproduction on the Proton from 800 to 1500 Mev
The Sigma beam asymmetry for positive pion photoproduction on the proton has
been measured over an angular range of 40-170 deg at photon energies from 0.8
to 1.5 GeV. The resulting data set includes 237 accurate points, 136 of these
belonging to an almost unexplored domain above 1.05 GeV. Data of such high
precision provide severe constraints for partial wave analyses. The influence
of this experiment on the GW multipole analysis is demonstrated. Significant
changes are found in multipoles connected to the S31(1620) and P13(1720)
resonances. Comparisons using the MAID analysis are also presented.Comment: 11 pages, 4 eps figures. to be published in Physics Letters
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