\title{Doubly Strange Hypernuclei Search in High Baryon Density Matter at STAR}

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    Yue-Hang Leung\textsuperscript{1} and Yingjie Zhou\textsuperscript{2} (for the STAR Collaboration)\vspace{0.2cm}\\
    \textsuperscript{2}GSI Helmholtzzentrum für Schwerionenforschung\\
    \textsuperscript{1}Heidelberg University
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The search for double-$\Lambda$ hypernuclei and strange dibaryons is crucial for understanding hyperon-hyperon interactions and strange matter in dense environments. Theoretical predictions suggest that weakly attractive $\Lambda$-$\Lambda$ interactions allow for the formation of stable $A = 5$ double-$\Lambda$ hypernuclei, while $A = 4$ is less likely to be particle-stable. Despite numerous experimental efforts, including those at J-PARC and KEK, conclusive evidence for the stability of double-$\Lambda$ hypernuclei with $A<6$ remains elusive. These searches also provide a pathway to exploring the possible existence of the H-dibaryon, a hypothesized six-quark state ($u\bar{u}d\bar{d}s\bar{s}$), whose discovery would offer significant insights into multi-strange interactions. In 2021, high-statistics data from Au+Au collisions at $\sqrt{s_{\rm NN}} = 3.0$ GeV were collected by the STAR experiment as part of the Beam Energy Scan II fixed-target program. The low energy collisions provide a high baryon density environment, which favors the formation of such exotic systems.


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In this talk, we will present the results on searches for the doubly strange systems using data from Au+Au collisions at $\sqrt{s_{\rm NN}} = 3.0$ GeV. We will present new results on searches for the following: $^{4}_{\Lambda\Lambda}\text{H}$ (${}_{\Lambda\Lambda}^{4}\text{H}\rightarrow {}^4_{\Lambda}\text{He}+\pi^-$, $^{4}_{\Lambda\Lambda}\text{H}\rightarrow {}^3_{\Lambda}\text{H}+p+\pi^-$), $^{4}_{\Lambda\Lambda}\text{n}$ ($^{4}_{\Lambda\Lambda}\text{n}\rightarrow {}^4_{\Lambda}\text{H}+\pi^-$), H-dibaryon (bound state: $\text{H} \rightarrow p+\pi+\Lambda $, resonance: $\text{H} \rightarrow \Lambda+\Lambda$, $\text{H} \rightarrow p+\Xi^-$). In the instances where no signal are found, upper limits for the production yield will be presented and compared with thermal model expectations, and the physics implications will be discussed.