Photo- and electroproduction of {eta} meson in the S{sub 11}(1535) region
Eta photo- and electroproduction are investigated within the effective Lagrangian formalism, wherein all significant contributions are taken into account to the amplitude at the tree level. These include the nucleon Born terms and the leading t-channel vector meson exchanges as the non-resonant piece. In addition, five resonance contributions in the s- and u-channel are considered; besides the dominant S{sub 11}(1535), these are: P/{sub 11}(1440), D/{sub 13}(1520), S/{sub 11}(1650) and P/{sub 11}(1710). The amplitude obtained shows that {pi}{sup o} and {eta} photo- and electroproduction near threshold have very significant differences, even as they share common contributions, such as those of the nucleon Born terms, the basis for the prediction of the low energy theorem (LET) for the {pi}{sub o} case. Among these differences, the contribution to {eta} photo- and electroproduction of the s-channel excitation of the S{sub 11}(1535) is the most significant. Fitting the model to the available data base has allowed us to extract the quantity {radical}{bar {sub {chi}}{Gamma}{sub {eta}}}A{sub 1/2}/{Gamma}{sub T}, characteristic of the photo- and electroexcitation of the S{sub 11}(1535) resonance and its decay into the {eta}-nucleon channel, of fundamental interest to future precision tests of hadron models and quantum chromodynamics. At the photon point, it is determined to be (2.23 {+-} 0.27) x 10{sup {minus}1} GeV{sup {minus}1}. Assuming a partial width {Gamma}{sub {eta}} of 75MeV, the helicity amplitude for S{sub 11}(1535) {yields} {gamma}p is obtained to be A{sub 1/2} = (96{+-}12)x10{sup {minus}3}GeV{sup {minus}1/2}, compared with latest6t quark4k model estimate of 76 and the results of the analysis of pion photoproduction yielding 74 {+-} 11, in the same units.
- Research Organization:
- Rensselaer Polytechnic Inst., Troy, NY (United States)
- OSTI ID:
- 121173
- Country of Publication:
- United States
- Language:
- English
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