Search

The reaction ep → e′ K+Σ0 has been investigated using a tree-level effective Lagrangian model previously employed by the author to study the γp → K+Σ0 reaction. In addition to the Born terms, the model incorporates a number of baryon resonances with spins up to 5/2 and the two kaon resonances,K*(892) andK1(1270).Momentum and energy dependent widths for the nucleon and Δ resonances are included by means of a dynamical model that makes use of empirical on-shell branching ratios. The model parameters are fit to a large pool of photoproduction data from the CLAS and GRAAL collaborations and electroproduction data from the CLAS collaboration. Photoproduction results are presented for the unpolarized differential cross section, the photon beam asymmetry Σ, the hyperon recoil asymmetry P, and the double polarization observables Cx and Cz. Electroproduction results are presented for the virtual photoproduction structure functions σU, σTT, σLT, and σLT′. The photoproduction results are compared with the CLAS and GRAAL photoproduction data and with the results of an earlier fit to just the photoproduction data, while the electroproduction results are compared with both recent and older CLAS electroproduction data. [ABSTRACT FROM AUTHOR]

The reaction γp→K+Σ0 has been investigated using a tree-level effective Lagrangian model similar to that employed previously by the author to study the electromagnetic production of Λ's from protons. In addition to the Born terms, the model incorporates a number of baryon resonances with spins up to 52 and the two kaon resonances, K*(892) and K1(1270). Momentum- and energy-dependent widths for the nucleon and Δ resonances are included by means of a dynamical model that makes use of empirical on-shell branching ratios. The model parameters, consisting of products of the coupling strengths at the electromagnetic and strong interaction vertices in the resonance contributions, are fit to a large pool of photoproduction data from the CLAS and GRAAL Collaborations. Results are presented for the unpolarized differential cross section, the photon beam asymmetry Σ, the hyperon recoil asymmetry P, and the double-polarization observables Cx and Cz in a variety of kinematical situations and compared with the data. [ABSTRACT FROM AUTHOR]

A model developed previously to investigate the electromagnetic production of strangeness from the proton is used to investigate single and double recoil polarization observables in the reaction ep→e'K+Λ in the relativistic impulse approximation. The formalism is based on a tree-level, effective Lagrangian model, which incorporates a variety of baryon resonances with spins up to 5/2 and the two kaon resonances, K*(892) and K1(1270). The parameters of the model were fit to a large pool of photoproduction data from the CLAS, GRAAL, SAPHIR, and LEPS collaborations and to CLAS data for the virtual photoproduction structure functions σU, σT, σL, σTT, σLT, and σLT'. Using two different versions of this model, results are presented for three recoil polarization asymmetries that have been measured recently at CLAS. A new fit is then presented which incorporates the new polarization data in the fitted data set. Results obtained with this new fit are presented for six recoil polarization asymmetries and compared with results from one of the previous fits. [ABSTRACT FROM AUTHOR]

A formalism is presented for the investigation of the reaction ed → e'K+ Λn in the relativistic impulse approximation. The formalism is based on a tree-level, effective Lagrangian model for the underlying virtual photoproduction reaction amplitude which incorporates a variety of baryon resonances with spins up to 5/2 and the two kaon resonances, K*(892) and K1(1270). The parameters of the model were fit to a large pool of proton photoproduction data from the CLAS, GRAAL, SAPHIR, and LEPS Collaborations and to CLAS data for the virtual photoproduction structure functions σU, σT, σL, σTT, σLT, and σLT'. The final-state Λn interaction is incorporated in the model by means of a three-dimensional overlap integral based on a simple phenomenological ?n potential. Results are presented for both the differential cross section, ds/dOK, and the double differential cross section, dσ/dΩK, for the virtual photoproduction of positive kaons and Λ's from the deuteron. [ABSTRACT FROM AUTHOR]

The beam polarization asymmetry in the reaction ep -> e'K+A has been investigated in a tree-level effective Lagrangian model. The model incorporates most of the well-established baryon resonances with spins up to 5/2, four less well-established nucleón resonances with larger mass, and the two kaon resonances K*(&92) and K 1(1270). The off-shell structure of the electromagnetic vertices was accounted for by the inclusion of electromagnetic form factors at those vertices. The free parameters of the model were fitted in a previous study to a large pool of photoproduction data from the CLAS, GRAAL, SAPHIR, and LEPS collaborations and to CLAS data for the virtual photoproduction structure functions su,sT,sL,sTT and sLT, Using this model, results were obtained for the beam polarization asymmetry structure function sLT, and compared with CLAS data. Two new fits to the combined photoproduction and electroproduction data with the sLT, data included were then generated. The first of these includes contributions from all of the resonances included in the previous study; the second excludes contributions from the /V(2080) and /V(2200) resonances. The results of both fits for both photoproduction and electroproduction observables are compared with the results of the previous fit and the data. [ABSTRACT FROM AUTHOR]

The reactions γp γ K+Δ and ep → e'K+A have been investigated in a tree-level effective Lagrangian model that incorporates most of the well-established baryon resonances with spins up to &frac52;, four less well-established nucléon resonances with larger mass, and the A"*(892) and AT 1(1270) resonances in the t channel. The off-shell structure of the electromagnetic vertices in electroproduction is incorporated by the addition of electromagnetic form factors. To achieve a good fit to the electroproduction data, it was found necessary to treat the ground-state hyperon form factors as adjustable parameters rather than simply equating them with the neutron form factors as was done in past studies. Photoproduction data consisting of unpolarized differential cross sections from the CLAS Collaboration, hyperon polarization asymmetries from CLAS, GRAAL, and SAPHIR, photon beam asymmetries from GRAAL and LEPS, and double polarization observables from CLAS were fit over the ΣK cm. energy range from threshold up to 2.3 GeV. Electroproduction data for the virtual photoproduction structure functions σu, σT, σL, σTT, and σLT from the CLAS collaboration were fit over the SAT cm. energy range from threshold up to 2.3 Gev and for several values of q2, the square of the virtual photon 4-momentum. For each intermediate resonance included, the fitted parameters in the photoproduction fit consist of the products of the coupling strengths at the electromagnetic and strong interaction vertices. In the electroproduction fit, there were, in addition, two form-factor parameters for each intermediate baryon in the J and u channels and one form factor parameter for each kaon resonance in the t channel. Results are presented for the fitted photoproduction and electroproduction observables and compared with the data for several sets of kinematical variables. [ABSTRACT FROM AUTHOR]