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

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.

arXiv commentTalk given at XIII workshop on high energy spin physics (DSPIN-09), Dubna, Russia, 1-5 September 2009