The role of hyperon resonances in p(γ, K+)Λ processes

Abstract

We discuss the role of hyperon resonances in the u-channel when modeling p γ, K + Λ processes in an effective Lagrangian approach. Without the introduction of hyperon resonances, one is forced to use soft hadronic form factors with a cutoff mass which is at best two times the kaon mass. After inclusion of the hyperon resonances in the u-channel, we obtain a fair description of the data with a cutoff mass of the order of 1.8 GeV.

P -wave excited baryons from pion- and photo-induced hyperon production

“…The physics at MAMI (among other data) has been closely followed by the MAID group of Drechsel and Tiator [131,132,133,134,135,136,137,138]. Smaller groups at Zagreb [139,140,141,142], Gent [143,144,145,146] and KVI made significant contributions to the field [147,148,149,150,151]. A few further papers are to be mentioned [152,153,154,155,156].…”

Decays of baryon resonances into ΛK+, ΣK+ and Σ+K0

“…Only the gross features of the data were reproduced. Two models based on similar effective Lagrangian approaches [22,23,24] gave the correct order of magnitude of the total cross section but failed to reproduce differential cross sections. A structure near 1.9 GeV was interpreted [23] as evidence for a 'missing' resonance + , Σ 0 K + and Σ + K 0 at this mass.…”

Constraints on background contributions fromK+Λelectroproduction

“…Note that the D 13 (1895) resonance is not listed in the Particle Data Group booklet [9] but is a candidate for a "new" resonance. A substantial improvement in the quality of the description of the p(γ, K + )Λ data was reached after including this resonance [10,11].…”

“…Both above mentioned manipulations amount to effectively reducing G K + Λp , either through adjusting the coupling constant or the hadronic form factor or a combination of both, thereby making assumptions which are rather questionable. Therefore, instead of adjusting the effective coupling G K + Λp , we have suggested an alternative procedure consisting of introducing hyperon resonances as a more natural mechanism to counterbalance the Born strength [11]. Those u-channel diagrams are observed to interfere destructively with the other background terms.…”