31st International Workshop on Deep Inelastic Scattering

Measurement of Λ hyperon spin-spin correlations in p+p collisions by the STAR experiment

9 avr. 2024, 15:10

20m

Maison MINATEC, Grenoble, FRANCE

Regular parallel talk WG5: Spin and 3D Structure WG5

Orateur

Jan Vanek (Brookhaven National Laboratory)

Description

About 50 years ago, it was discovered that $\mathrm{\Lambda }$ hyperons are produced polarized in collisions of unpolarized protons on beryllium. Since then, the $\mathrm{\Lambda }$ polarization has been observed in various collision systems, including $e^{+}$+$e^{-}$ collisions. Majority of current results indicate the importance of final state effects, such as hadronization or fragmentation, in polarization of the $\mathrm{\Lambda }$ hyperons. A recently proposed technique for the investigation of the $\mathrm{\Lambda }$ hyperon polarization is a measurement of $\mathrm{\Lambda }\overline{\mathrm{\Lambda }}$, $\mathrm{\Lambda }\mathrm{\Lambda }$, and $\overline{\mathrm{\Lambda }}\overline{\mathrm{\Lambda }}$ spin-spin correlations. This technique is expected to help understand if the $\mathrm{\Lambda }$ polarization has any contribution from the early stage of the $p$+$p$ collisions, e.g., from initial state parton spin correlation, or if it is exclusively a final state effect.

In this presentation, we present the preliminary results of the $\mathrm{\Lambda }\mathrm{\Lambda }$, $\overline{\mathrm{\Lambda }}\overline{\mathrm{\Lambda }}$, and $\mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ spin-spin correlations in $p$+$p$ collisions at $\sqrt{s}=200\text{GeV}$ collected by the STAR experiment in 2012. The $\mathrm{\Lambda }$ and $\overline{\mathrm{\Lambda }}$ candidates are reconstructed at mid-rapidity ($|y|<1$) with transverse momentum in range of $0.5<p_{\mathrm{T}}<5.0\mathrm{GeV}/c$. This measurement will provide additional insight into the importance of the initial state effects for the $\mathrm{\Lambda }$ hyperon polarization.

Documents de présentation

DIS_2024_Vanek_final.pdf