Abstract
The photoproduction reaction of $\ensuremath{\gamma}p\ensuremath{\rightarrow}{K}^{+}\mathrm{\ensuremath{\Lambda}}(1405)$ is investigated based on an effective Lagrangian approach at the tree-level approximation with the purpose of understanding the reaction mechanism and extracting the resonance contents and the associated resonance parameters in this reaction. Apart from the $t$-channel $K$ and ${K}^{*}$ exchanges, $s$-channel nucleon ($N$) exchange, $u$-channel $\mathrm{\ensuremath{\Sigma}}, \mathrm{\ensuremath{\Lambda}}$, and $\mathrm{\ensuremath{\Lambda}}(1405)$ exchanges, and generalized contact term, the exchanges of a minimum number of $N$ resonances in the $s$ channel are taken into account in constructing the reaction amplitudes to describe the experimental data. It is found that by introducing the $N(2000){5/2}^{+}$ resonance exchange in the $s$ channel, one can reproduce the most recent differential cross-section data from the CLAS Collaboration quite well. Further analysis shows that the cross sections of $\ensuremath{\gamma}p\ensuremath{\rightarrow}{K}^{+}\mathrm{\ensuremath{\Lambda}}(1405)$ at high energies are dominated by the $t$-channel $K$ exchange, while the contributions from the $s$-channel $N$ and $N(2000){5/2}^{+}$ exchanges are rather significant to the cross sections in the near-threshold energy region. Predictions for the beam and target asymmetries for $\ensuremath{\gamma}p\ensuremath{\rightarrow}{K}^{+}\mathrm{\ensuremath{\Lambda}}(1405)$ are given.
Highlights
The study of nucleon resonances (N∗’s) has always been of great interest in hadron physics, as a deeper understanding of baryon resonances is essential to get insight into the nonperturbative regime of quantum chromodynamics (QCD)
Lagrangians, the resonance propagator, and the phenomenological form factors employed in the present work
The products of the coupling constants g(RiN) γ gR ∗K (i = 1, 2), which are relevant to the amplitudes of γ p → K+ (1405), are treated as fit parameters in the present work due to the lack of experimental information on the resonance N (2000)5/2+ decay
Summary
The study of nucleon resonances (N∗’s) has always been of great interest in hadron physics, as a deeper understanding of baryon resonances is essential to get insight into the nonperturbative regime of quantum chromodynamics (QCD). [13] shows that the required resonance contribution in K∗ photoproduction is from the (1905)5/2+ resonance exchange and the cross sections of γ p → K∗ are rather small around W ≈ 2.1 GeV In this case, the effects of the K∗ intermediate state on the γ p → K+ (1405) reaction, which is regarded as a triangle singularity mechanism in. The scattered symbols are data from the CLAS Collaboration [14] We analyze the available differential cross-section data from the CLAS Collaboration [14] for the γ p → K+ (1405) reaction within an effective Lagrangian approach at the tree-level approximation.
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