Analysis of data for γp → f1(1285)p photoproduction

The photoproduction of the f1(1285)meson off the proton target is investigated within an effective Lagrangian approach.The t-channelρ-andω-exchange diagrams,u-channel nucleon-exchange diagram,generalized contact term,and s-channel pole diagrams of the nucleon and a minimal number of nucleon resonances are taken into account in constructing the reaction amplitudes to describe the experimental data.Three different models,that is,the Feynman,Regge,and interpolated Regge models,are employed,where the t-channel reaction amplitudes are constructed in Feynman,Regge,and interpolated Regge types,respectively.The results show that neither the Feynman model with two nucleon resonances nor the interpolated Regge model with one nucleon resonance can satisfactorily reproduce the available data forγp→f1(1285)p.Nevertheless,in the Regge model,when any one of the N(1990)7/2^(+),N(2000)5/2^(+),N(2040)3/2^(+),N(2060)5/2^(-),N(2100)1/2^(+),N(2120)3/2^(-),N(2190)7/2^(-),N(2300)1/2^(+),and N(2570)5/2^(-)resonances is considered,the data can be well described.The resulting resonance parameters are consistent with those advocated in the Particle Data Group(PDG)review.Further analysis shows that,in the high-energy region,the peaks of γp→f1(1285)p differential cross sections at forward angles are dominated by the contributions from t-channelρ-andω-exchange diagrams,while in low-energy region,the s-channel pole diagrams of resonances also provide significant contributions to theγp→f1(1285)p cross sections.

Photo-production of lowest∑^(*)_(1/2) state within the Regge-effective Lagrangian approach

Because the lowest ∑^(*) state with quantum numbers spin-parity J^(P)=1/2-is far from being established experimentally and theoretically,we perform a theoreticalstudy on the ∑^(*)_(1/2)-photo-production within the Regge-effective Lagrangian approach.Considering that ∑^(*)_(1/2)-couples to the KN channel,westudy the contributions from the t-channel K^(*) exchange diagram.Moreover,the contributions from the t-channel K^(*) exchange,s-channel nucleon pole,u-channel 2 exchange,and contact term are considered.The differential and total cross sections of the processγn→K+∑^(*)_(1/2)-are predicted with our model parameters.The results should help in experimentaly searching for the ∑^(*)_(1/2)-state in the future.

Photoproduction reactionγn→K^(*0)∧in an effective Lagrangian approach

In our previous work[Phys.Rev.C 101,014003(2020)],the photoproduction reactionγp→K^(*+)Λwas investigated within an effective Lagrangian approach.The reaction amplitudes were constructed by including the t-channel K,K^(*),and k exchanges,u-channelΛ,∑,and∑^(*)exchanges,s-channel N,N(2000)5/2^(+),and N(2060)5/2^(-)exchanges,and interaction current.The data on the differential cross sections and spin density matrix elements were described simultaneously.In this study,we investigate the photoproduction reactionγn→K^(*0)Λbased on the same reaction mechanism as that ofγp→K^(*+)Λto obtain a unified description of the data forγp→K^(*+)Λandγn→K^(*0)Λwithin the same model.All hadronic coupling constants,form factor cutoffs,and the resonance masses and widths in the present calculations remain the same as in our previous work forγp→K^(*+)Λ.The available differential cross-section data forγn→K^(*0)Λare well reproduced.Further analysis shows that the cross sections ofγn→K^(*0)Λare dominated by the contributions of the t-channel K exchange,while the s-channel N(2000)5/2+and N(2060)5/2-exchanges also provide considerable contributions.

Photoproductionγp→K^(+)Λ(1690)in an effective Lagrangian approach

A gauge-invariant model is constructed for theγp→K^(+)Λ(1690)reaction within a tree-level effective Lagrangian approach to understand the underlying production mechanisms and study the resonance contributions in this reaction.In addition to the t-channel K and K^(∗)exchanges,s-channel nucleon exchange,and interaction current,the s-channel nucleon resonance exchanges are included in constructing the reaction amplitudes to describe the data.It is found that the contributions from the s-channel N(2570)5/2^(−)exchange are required to describe the most recently measured total cross-section data forγp→K^(+)Λ(1690)from the CLAS Collaboration.Further analysis indicates that the interaction current dominates the γ p→K^(+)Λ(1690)reaction near the threshold as a result of gauge invariance.The t-channel K exchange contributes significantly,while the contributions from the t-channel K^(∗)exchange and s-channel nucleon exchange are ultimately negligible.The contributions from the s-channel N(2570)5/2^(−)exchange are found to be responsible for the bump structure shown in the CLAS total cross-section data above the center-of-mass energy W≈2.7 GeV.The predictions of the differential cross sections forγp→K^(+)Λ(1690)are presented and discussed,which can provide theoretical guidance for future experiments.