Off-shell effects in the electromagnetic production of strangeness

Abstract

Previous approaches to the photo- and electro-production of strangeness off the proton, based upon effective hadronic Lagrangians, are extended here to incorporate the so called off-shell effects inherent to the fermions with spin >= 3/2. A formalism for intermediate-state, spin 3/2, nucleonic and hyperonic resonances is presented and applied to the processes $\gamma + p ---> K^{+} + \Lambda$, for $E_{\gamma}^{lab}$ <= 2.5 GeV, $e + p ---> e' + K^+ + \Lambda$, as well as the branching ratio for the crossed channel reaction $K^- + p ---> \gamma + \Lambda$, with stopped kaons. The sensitivity, from moderate to significant, of various observables to such effects are discussed.Comment: 38 pages in LaTeX2e-RevTeX + 8 postscript figure

Kaon electromagnetic production: constraints set by new data

“…The Saclay-Lyon models SL [2] and SLA [3] describe satisfactorily the old data except at θ cm K > 130 deg and E lab γ > 1.5 GeV [1]. The models include nucleon resonances with spin up to 3/2 (SLA) and 5/2 (SL) and many hyperon ones.…”

“…Moreover, we consider also the D 13 (1895) one predicted by the quark model and already assumed in the Kaon-MAID model [4] but reliably not observed yet. The spin 3/2 and 5/2 resonances are treated in the method used in [2] without off-shell effects [3].…”

“…Most of the models have, however, problems with a reasonable description of new experimental data collected in JLab and Bonn [1]. Among the models which can still provide a satisfactory prediction in comparison with new data are the latest isobaric ones, Saclay-Lyon [2,3], Kaon-MAID [4], and Janssen et al [5].…”

Photoproduction of K+Λ and K0Λ on Deuteron

“…Among theoretical investigations, the most successful ones in the low energy region are isobar models such as the Saclay-Lyon A (SLA) model [1] and the Kaon MAID (KM) model [2]. They include resonances of nucleons, hyperons and mesons in the effective Lagrangian.…”

Strangeness production on the nucleon

“…This work marked the start of a long series of theoretical efforts in this field [8][9][10][11][12][13][14][15][16]. The earliest works clearly lacked the presence of a reliable database.…”