Longitudinal spin transfer of Lambda and anti-Lambda in polarized pp 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 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)$forinclusive$Λ$and$D_{LL} = -0.12 \pm 0.08(stat) \pm 0.03(syst)$forinclusive$\barΛ$hyperonswith$<eta> = 0.5$and$<p_T> = 3.7 GeV/c$. The prospects with 2009 data and the future measurements are also given.

6 pages, 3 figures, presentation at the SPIN2010 International Symposium, Juelich (Germany), Sep. 27-Oct. 2, 2010

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