Photoproduction reaction $\gamma n \to K^{\ast 0}\Lambda$ in an effective Lagrangian approach

TL;DR

This study extends an effective Lagrangian model to analyze the photoproduction reaction $oldsymbol{\gamma n o K^{ ext{*} 0}\Lambda}$, successfully describing experimental data and identifying dominant reaction mechanisms.

Contribution

It provides a unified theoretical description of both $oldsymbol{\gamma p o K^{ ext{*} +}\Lambda}$ and $oldsymbol{\gamma n o K^{ ext{*} 0}\Lambda$ reactions using the same model parameters.

Findings

Differential cross sections are well reproduced.

$t$-channel $K$ exchange dominates the reaction.

$s$-channel nucleon resonances contribute significantly.

Abstract

In our previous work [Phys. Rev. C 101, 014003 (2020)], the photoproduction reaction $\gamma p \to K^{\ast +} \Lambda$ has been investigated within an effective Lagrangian approach. There, the reaction amplitudes were constructed by including the $t$-channel $K$, $K^\ast$, and $\kappa$ exchanges, the $u$-channel $\Lambda$, $\Sigma$, and $\Sigma^\ast$ exchanges, the $s$-channel $N$, $N(2000)5/2^+$, and $N(2060)5/2^-$ exchanges, and the interaction current. It has been shown that the data on both the differential cross sections and the spin density matrix elements were simultaneously and satisfactorily described. In this paper, we study the photoproduction reaction $\gamma n \to K^{\ast 0} \Lambda$ based on the same reaction mechanism as that of $\gamma p \to K^{\ast +} \Lambda$ with the purpose of getting a unified description of the data for both $\gamma p \to K^{\ast +} \Lambda$ and $\gamma n \to K^{\ast 0} \Lambda$ within a 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 for $\gamma p \to K^{\ast +} \Lambda$. The available differential cross-section data for $\gamma n \to K^{\ast 0} \Lambda$ are well reproduced. Further analysis shows that the cross sections of $\gamma n \to K^{\ast 0} \Lambda$ are dominated by the contributions of the $t$-channel $K$ exchange, while the $s$-channel $N(2000)5/2^+$ and $N(2060)5/2^-$ exchanges provide considerable contributions as well.