Longitudinal Spin Transfer to $\Lambda$ and $\bar{\Lambda}$ in Polarized Proton-Proton Collisions at $\sqrt{s} = 200 Gev at Star

TL;DR

This paper measures the longitudinal spin transfer to Lambda and anti-Lambda hyperons in polarized proton-proton collisions at 200 GeV, providing insights into spin dynamics in high-energy QCD processes.

Contribution

It presents the first measurement of longitudinal spin transfer to hyperons at RHIC energies, expanding understanding of spin transfer mechanisms in polarized proton collisions.

Findings

Longitudinal spin transfer D_LL is close to zero within uncertainties.

Results are consistent with certain theoretical models of spin transfer.

Provides baseline data for future transverse spin transfer studies.

Abstract

We report our measurement on longitudinal spin transfer, $D_{LL}$, from high energy polarized protons to $\Lambda$ and $\bar{\Lambda}$ hyperons in proton-proton collisions at $\sqrt{s} = 200GeV$ with the STAR detector at RHIC. The measurements cover $\Lambda$, $\bar\Lambda$ pseudorapidity $|\eta| < 1.2$ and transverse momenta $p_T$ up to $4GeV/c$. The longitudinal spin transfer is found to be $D_{LL}= -0.03\pm 0.13(stat) \pm 0.04(syst)$ for inclusive $\Lambda$ and $D_{LL} = -0.12 \pm 0.08(stat) \pm 0.03(syst)$ for inclusive $\bar{\Lambda}$ hyperons with $<\eta> = 0.5$ and $<p_T> = 3.7GeV/c$. The prospect on transverse spin transfer measurement is also given.