The researchers analyzed the new experimental data of the Λ(1520) and Σ(1385) photoproductions off a proton target released by the CLAS Collaboration at JLab recently. Based on the analysis, the internal structure of the nucleon resonance around 2 GeV was studied. 

The study of nucleon resonances is an important topic in hadron physics. The most important way to study the nucleon resonances is the collision of the photon and nucleon. The knowledge about the nucleon resonances around 2 GeV is still scarce. Recently, the CLAS Collaboration released their new high-precision data about the cross section of the Σ(1385) and Λ(1520) photoproduction. Due to the high threshold, the new data is very helpful to the study of the nucleon resonances around 2 GeV. 

 On the basis of the constituent quark model as shown in Fig. 1 and Fig. 2 , the researchers fitted the new CLAS data. In Σ(1835) photoproduction, the contributions from Δ(2000) count more important than these from other nucleon resonances, and the N(2120) is dominant in the Λ(1520) photoproduction. The data support that the Δ(2000) and N(2120) is the third Δ state with spin-parity 5/2⁺ and the third nucleon state with spin-parity 3/2^- in constituent quark model, respectively. Other nucleon resonances are found to make negligible contributions in the channel considered in this work.  

The results are helpful to understand the internal structure of the nucleon resonance around 2 GeV and the “missing resonance” problem. 

The results have been published in Phys. Rev. C89: 055204(2014), Nucl. Phys. A927:24(2014) 

The article can be linked as follows:  

http://journals.aps.org/prc/abstract/10.1103/PhysRevC.89.055204 

http://www.sciencedirect.com/science/article/pii/S0375947414000669 

Fig.1 The differential cross section for the Σ(1385) photoproduction

Fig.2 The differential cross section for the Σ(1520) photoproduction