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

We report our measurement on longitudinal spin transfer, D_LL, from high energy polarized protons to $Λ$ and $\barΛ$ hyperons in proton-proton collisions at $\sqrt{s} = 200 GeV$ with the STAR detector at RHIC. The current measurements cover $Λ$, $\barΛ$ pseudorapidity $|η| < 1.2$ 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 $Λ$ and $D_{LL} = -0.12 \pm 0.08(stat) \pm 0.03(syst)$ for inclusive $\barΛ$ hyperons with $<eta> = 0.5$ and $<p_T> = 3.7 GeV/c$. The prospects with 2009 data and the future measurements are also given.