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

TL;DR

This paper reports the first measurement of the longitudinal spin transfer from polarized protons to Lambda and anti-Lambda hyperons in high-energy proton-proton collisions at 200 GeV, providing new insights into spin dynamics.

Contribution

It introduces the first measurement of $D_{LL}$ in proton-proton collisions at this energy, expanding understanding of spin transfer mechanisms in high-energy physics.

Findings

$D_{LL}$ for $Lambda$ is approximately -0.03 with uncertainties.

$D_{LL}$ for $ar{Lambda}$ is approximately -0.12 with uncertainties.

Results show no strong dependence on $eta$ or $p_T$ within uncertainties.

Abstract

The longitudinal spin transfer, $D_{LL}$, from high energy polarized protons to $\Lambda$ and $\bar{\Lambda}$ hyperons has been measured for the first time in proton-proton collisions at $\sqrt{s} = 200 \mathrm{GeV}$ with the STAR detector at RHIC. The measurements cover pseudorapidity, $\eta$, in the range $|\eta| < 1.2$ and transverse momenta, $p_\mathrm{T}$, up to $4 \mathrm{GeV}/c$. The longitudinal spin transfer is found to be $D_{LL}= -0.03\pm 0.13(\mathrm{stat}) \pm 0.04(\mathrm{syst})$ for inclusive $\Lambda$ and $D_{LL} = -0.12 \pm 0.08(\mathrm{stat}) \pm 0.03(\mathrm{syst})$ for inclusive $\bar{\Lambda}$ hyperons with $<\eta> = 0.5$ and $<p_\mathrm{T}> = 3.7 \mathrm{GeV}/c$. The dependence on $\eta$ and $p_\mathrm{T}$ is presented.