Measurement of $\Lambda$ hyperon spin-spin correlations in p+p collisions by the STAR experiment

TL;DR

This paper proposes a new experimental method to measure spin-spin correlations of Lambda hyperons in proton-proton collisions, aiming to clarify the origin of hyperon polarization observed in various collision systems.

Contribution

It introduces a novel approach utilizing pair spin-spin correlations to distinguish between initial and final state effects in hyperon polarization.

Findings

Feasibility of measuring Lambda pair spin correlations in p+p collisions at 200 GeV.

Potential to differentiate early stage from hadronization effects on polarization.

Analysis of STAR 2012 data suggests sufficient statistics for this measurement.

Abstract

Polarization of $\Lambda$ hyperons has been observed in various collision systems over a wide range of collision energies over the last 50 years since its discovery in Fermilab in the 70's. The existing experimental and theoretical techniques were not able to provide a conclusive answer about the origin of the polarization. In these proceedings, we discuss the possibility to use a new experimental method which utilizes measurement of $\Lambda\bar{\Lambda}$, $\Lambda\Lambda$, and $\bar{\Lambda}\bar{\Lambda}$ pair spin-spin correlations. With this new approach, it should be possible to distinguish if the polarization originates from early stage effects, such as initial state parton spin correlation, or if it is a final state effect originating from hadronization. Furthermore we, study the feasibility to perform this measurement in $p+p$ collisions at $\sqrt{s} = 200$~GeV collected by STAR in 2012 which should provide sufficient statistics of $\Lambda\bar{\Lambda}$, $\Lambda\Lambda$, and $\bar{\Lambda}\bar{\Lambda}$ pairs to perform this measurement.