Longitudinal spin transfer of Lambda and anti-Lambda in polarized pp collisions at \sqrt s=200 GeV at STAR

TL;DR

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

Contribution

The study presents the first measurements of D_LL for Lambda and anti-Lambda hyperons at RHIC energies, expanding understanding of spin transfer mechanisms in polarized proton collisions.

Findings

D_LL for Lambda: -0.03 ± 0.13 (stat) ± 0.04 (syst)

D_LL for anti-Lambda: -0.12 ± 0.08 (stat) ± 0.03 (syst)

Results are consistent with zero within uncertainties.

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 $\sqrt{s} = 200 GeV$ with the STAR detector at RHIC. The current measurements cover $\Lambda$, $\bar\Lambda$ pseudorapidity $|\eta| < 1.2$ and transverse momenta $p_T$ up to $4GeV/c$ using the data taken in 2005. 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 $<p_T> = 3.7 GeV/c$. The prospects with 2009 data and the future measurements are also given.