Photoproduction γp→K+Λ(1520) in an effective Lagrangian approach

Neng-Chang Wei,Yu Zhang,Fei Huang,De-Min Li

doi:10.1103/physrevd.103.034007

Neng-Chang Wei, Yu Zhang + Show 2 more

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https://doi.org/10.1103/physrevd.103.034007

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Abstract

The data on differential cross sections and photon-beam asymmetries for the $\gamma p \to K^+\Lambda(1520)$ reaction have been analyzed within a tree-level effective Lagrangian approach. In addition to the $t$-channel $K$ and $K^\ast$ exchanges, the $u$-channel $\Lambda$ exchange, the $s$-channel nucleon exchange, and the interaction current, a minimal number of nucleon resonances in the $s$ channel are introduced in constructing the reaction amplitudes to describe the data. The results show that the experimental data can be well reproduced by including either the $N(2060)5/2^-$ or the $N(2120)3/2^-$ resonance. In both cases, the contact term and the $K$ exchange are found to make significant contributions, while the contributions from the $K^\ast$ and $\Lambda$ exchanges are negligible in the former case and considerable in the latter case. Measurements of the data on target asymmetries are called on to further pin down the resonance contents and to clarify the roles of the $K^\ast$ and $\Lambda$ exchanges in this reaction.

Highlights

The traditional πN elastic and inelastic scattering experiments have provided us with abundant knowledge of the mass spectrum and decay properties of the nucleon resonances (NÃ’s)
Different groups gave quite different answers for the following questions: Are the contributions from the t-channel KÃ exchange and u-channel Λ exchange significant or not in this reaction, are the nucleon resonances introduced in the s channel indispensable or not to describe the available data, and, if yes, what are the resonance contents and their associated parameters in this reaction? On the other hand, we notice that even though the data on photon-beam asymmetries for γp → KþΛð1520Þ have been reported by the LEPS Collaboration in 2010, they have never been well reproduced in previous theoretical publications of Refs. [11,12,13,14,15,16,17,18,19,20]
The photoproduction reaction γp → KþΛð1520Þ is of interest, since the KþΛð1520Þ has isospin 1=2, excluding the contributions of the Δ resonances from the reaction mechanisms, and the threshold of KþΛð1520Þ is at 2.01 GeV, making this reaction more suitable than π production reactions to study the nucleon resonances in a less-explored higher resonance mass region

Summary

Introduction

The traditional πN elastic and inelastic scattering experiments have provided us with abundant knowledge of the mass spectrum and decay properties of the nucleon resonances (NÃ’s). Both the quark model [1,2] and lattice QCD [3,4] calculations predict more resonances than have been observed in the πN scattering experiments. The resonances predicated by quark model or lattice QCD but not observed in experiments are called “missing resonances,” which are supposed to have small couplings to the πN channel and, escape from experimental detection. We focus on the γp → KþΛð1520Þ reaction process. The threshold of the KþΛð1520Þ photoproduction is about 2.01 GeV, and, this reaction

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