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Theta^+ baryon production in KN and NN reactions

We study $Θ^+(1540)$ productions in kaon-nucleon ($KN$) and nucleon-nucleon ($NN$) interactions by assuming that the $Θ^+$ is an isosinglet with $J^P = \frac12^+$. Possible $t$-channel diagrams with $K^*$ exchange are considered in both reactions as well as $K$ exchange in $NN$ reaction. The cross section for $np \to Λ^0 Θ^+$, which has not been considered in previous calculations, is found to be about a factor of 5 larger than that for $np \to Σ^0 Θ^+$ due to the large coupling of $KNΛ$ interaction. The cross sections are obtained by setting $g_{KNΘ}^{}=1$ and varying the ratio of $g_{K^*NΘ}^{}/g_{KNΘ}^{}$ so that future experimental data can be used to estimate these couplings. We also find that the isospin relations hold for these reactions.