Search for Kaonic Nuclear Clusters in Nuclear Collisions with FOPI

Recently, exotic nuclear systems involving a $\bar{K}$, ($K^-$ or $\bar{K}^0$) as constituent (such as $ppK^-$, $ppnK^-$, $pppK^- $, $pppnK^-$ and $ppnnK^-$) were predicted by Akaishi and Yamazaki to have narrow discrete bound states with large biding energies as much as 100 MeV due to the strong $K^{-}-p$ attraction, which may lead the system to have a much higer density than normal nuclear density. We produce and identify such $\bar{K}$ clusters in heavy-ion collision or proton induced reactions by making use of the capability of the FOPI detector at GSI which is enable to reconst invariant-mass from all the charged trajectories of the decay particles of K clusters such as $ppK\rightarrow \Lambda +p$, $ppnK\rightarrow \Lambda+d$ and $pppK\rightarrow \Lambda+p+p$. $ppK^-$ is produced with proton induced reaction on $d$ target as $p+d \rightarrow [\Lambda(1405)+p] + K^0 + p \rightarrow ppK^- + K^0 + p$, where $\Lambda(1405) \equiv pK^- / n\bar{K}^0$ works as a doorway to form $\bar{K}$ cluster. We can identify the $ppK^-$ in the missing mass spectrum, and simultaneously study its decay pattern by invariant mass method. With light nuclear target more heavier $\bar{K}$ clusters can be produced by $\Lambda(1405)$ production and successive $\bar{K}$ transfer / knock-on reactions.