Speaker
Description
Collective flow has been commonly used for studying the properties of matter created in high-energy heavy-ion collisions, due to its high sensitivity on early stage collision dynamics. The first-order Fourier coefficient of azimuthal distributions of produced particles $v_1$, also called directed flow, has been analyzed for different particle species from the lightest mesons to light nuclei in such collisions. In this talk, we report $^3_{\Lambda}$H reconstruction from its two-body and three-body pionic decay channels, and $^4_{\Lambda}$H reconstruction from its two-body pionic decay channel. Then, the first observation of the hyper-nuclei $^3_{\Lambda}$H and $^4_{\Lambda}$H directed flow $v_1$ from $\sqrt{s_{NN}}=$ 3 GeV mid-central (5–40%) Au+Au collisions at RHIC will be presented. The directed flow of $^3_{\Lambda}$H and $^4_{\Lambda}$H are compared with those of the copiously produced particles such as p, $\Lambda$, d, t,$^3$He and $^4$He. It is observed that the slopes of $v_1$ at midrapidity for the hyper-nuclei $^3_{\Lambda}$H and $^4_{\Lambda}$H follow a baryon number scaling implying that coalescence process is a dominant mechanism for the hyper-nuclei production in these collisions. Hypernuclei directed flow measurement would shed light on the hyperon-nucleon (YN) interaction in condensed nuclear medium with finite pressure.
