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

Abstract

The longitudinal spin transfer, $D_{LL}$, from high energy polarized protons to $Λ$ and $\barΛ$ 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, $η$, in the range $|η| < 1.2$ 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 $Λ$ and $D_{LL} = -0.12 \pm 0.08(\mathrm{stat}) \pm 0.03(\mathrm{syst})$ for inclusive $\barΛ$ hyperons with $<η> = 0.5$ and $<p_\mathrm{T}> = 3.7 \mathrm{GeV}/c$. The dependence on $η$ and $p_\mathrm{T}$ is presented.

5 pages, 4 figures