Speaker
Description
The transverse polarization of $\Lambda$/$\bar{\Lambda}$ in unpolarized hadron-hadron reactions, first observed decades ago, is still not fully understood. The polarizing fragmentation functions (pFFs), which give rise to the $\Lambda$/$\bar{\Lambda}$ polarization, can be investigated by measuring the $\Lambda$/$\bar{\Lambda}$ transverse polarization inside jets. In this contribution, we will present the measurements of $\Lambda$/$\bar{\Lambda}$ polarization within jets in $p$+$p$ collisions at $\sqrt{s} =$ 200 and 510 GeV, as well as in $p$+Au collisions at $\sqrt{s_{NN}}=$ 200 GeV collected by the STAR experiment at RHIC. Measurements at different collision energies in $p$+$p$ collisions can probe the energy scale dependence of the polarization, while comparisons between $p$+$p$ and $p$+Au collisions explore possible cold nuclear medium effects. These measurements provide a critical test of the universality of pFFs and offer new insights into the mechanisms behind the $\Lambda$/$\bar{\Lambda}$ polarization.
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