Rutherglen, J.G.
GAMMA P --> ETA P
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Measurement of the beam asymmetry in eta photoproduction off the proton.

The CBELSA & TAPS collaborations Elsner, D. ; Anisovich, A.V. ; Anton, G. ; et al.
Eur.Phys.J.A 33 (2007) 147-155, 2007.
Inspire Record 744568 DOI 10.17182/hepdata.43430

The beam asymmetry, $\Sigma$, was measured at ELSA in the reaction $\vec \gamma p \to \eta p$ using linearly polarised tagged photon beams, produced by coherent bremsstrahlung off a diamond. The crystal was oriented to provide polarised photons in the energy range $E_\gamma = 800$ to 1400 MeV with the maximum polarisation of $P_\gamma = 49$ % obtained at 1305 MeV. Both dominant decay modes of the $\eta$ into two photons and $3\pi^0$ were used to extract the beam asymmetry from the azimuthal modulation of the cross section. The measurements cover the angular range $\Theta_\text{cm}\simeq 50$ -- 150 degrees. Large asymmetries up to 80 % are observed, in agreement with a previous measurement. The eta-MAID model and the Bonn--Gatchina partial wave analysis describe the measurements, but the required partial waves differ significantly.

6 data tables
Table 1

Photon asymmetry for eta photoproduction at incident photon energy of 850 MeV.

Table 2

Photon asymmetry for eta photoproduction at incident photon energy of 950 MeV.

Table 3

Photon asymmetry for eta photoproduction at incident photon energy of 1050 MeV.

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The Polarized Target Asymmetry in Photoproduction of $\Eta$ Mesons From Protons at 4-{GeV}

Bussey, P.J. ; Raine, C. ; Rutherglen, J.G. ; et al.
Nucl.Phys.B 185 (1981) 269-273, 1981.
Inspire Record 155784 DOI 10.17182/hepdata.34276

Measurements have been made of the polarised target asymmetry parameter T for eta photoproduction from protons at a photon energy of 4 GeV and t -values of −0.4, −0.6 and −0.8 (GeV/ c ) 2 . The results are compared with predictions for this quantity.

1 data table
Table 1

No description provided.


The Polarized Beam Asymmetry in Photoproduction of eta Mesons from Protons at 2.5-GeV and 3.0-GeV

Bussey, P.J. ; Raine, C. ; Rutherglen, J.G. ; et al.
Phys.Lett.B 61 (1976) 479-482, 1976.
Inspire Record 108515 DOI 10.17182/hepdata.27687

Measurements of the polarised beam asymmetry parameter Σ for eta photoproduction from protons, have been carried out at incident energies of 2.5 GeV and 3.0 GeV, and for various t -values between −0.2 (GeV/c) 2 and −1.2 (GeV/c) 2 . The values of Σ are close to +1 for values of | t | less than 0.7 (GeV/c) 2 , showing that there can be little contribution from unnatural parity exchange in any Regge exchange model of the process, in disagreement with present theories. Differential cross sections for the process werre also measured, and are consistent with those from other experiments.

2 data tables
Table 1

No description provided.

Table 2

No description provided.