14 research outputs found
Photoproduction of eta mesons from the neutron: cross sections and double polarization observable E
Photoproduction of mesons from neutrons} \abstract{Results from
measurements of the photoproduction of mesons from quasifree protons and
neutrons are summarized. The experiments were performed with the CBELSA/TAPS
detector at the electron accelerator ELSA in Bonn using the
decay. A liquid deuterium target was used for the
measurement of total cross sections and angular distributions. The results
confirm earlier measurements from Bonn and the MAMI facility in Mainz about the
existence of a narrow structure in the excitation function of . The current angular distributions show a forward-backward
asymmetry, which was previously not seen, but was predicted by model
calculations including an additional narrow state. Furthermore, data
obtained with a longitudinally polarized, deuterated butanol target and a
circularly polarized photon beam were analyzed to determine the double
polarization observable . Both data sets together were also used to extract
the helicity dependent cross sections and . The
narrow structure in the excitation function of
appears associated with the helicity-1/2 component of the reaction
Central-local government relations in the 1980s Glasgow and Liverpool compared
SIGLEAvailable from British Library Document Supply Centre- DSC:D187784 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Polarization observables in double neutral pion photoproduction
Measurements of target asymmetries and double-polarization observables for
the reaction are reported. The data were taken with
the CBELSA/TAPS experiment at the ELSA facility (Bonn University) using the
Bonn frozen-spin butanol (CHOH) target, which provided transversely
polarized protons. Linearly polarized photons were produced via bremsstrahlung
off a diamond crystal. The data cover the photon energy range from
=650 MeV to =2600 MeV and nearly the complete angular
range. The results have been included in the BnGa partial wave analysis.
Experimental results and the fit agree very well. Observed systematic
differences in the branching ratios for decays of and
resonances are attributed to the internal structure of these excited nucleon
states. Resonances which can be assigned to SU(6)O(3) two-oscillator
configurations show larger branching ratios to intermediate states with
non-zero intrinsic orbital angular momenta than resonances assigned to
one-oscillator configurations.Comment: 21 pages, 27 figure
Measurement of the helicity asymmetry
A measurement of the double-polarization observable E for the reaction is reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility in Bonn using the Bonn frozen-spin butanol (CHOH) target, which provided longitudinally-polarized protons. Circularly-polarized photons were produced via bremsstrahlung of longitudinally-polarized electrons. The data cover the photon energy range from to 2310Â MeV and nearly the complete angular range. The results are compared to and have been included in recent partial wave analyses
Observation of a structure in the M-p eta invariant mass distribution near 1700 MeV/c(2) in the gamma p -> p pi(0)eta reaction
The reaction gamma p -> p pi(0)eta has been studied with the CBELSA/TAPS detector at the electron stretcher accelerator ELSA in Bonn for incident photon energies from threshold up to 3.1 GeV. This paper has been motivated by the recently claimed observation of a narrow structure in the MN n invariant mass distribution at a mass of 1678 MeV/c(2). The existence of this structure cannot be confirmed in the present work. Instead, for E-gamma = 1400-1500 MeV and the cut M-P pi(0) pa(0) -> p pi(0)eta reaction