在200GeV极化质子质子对撞中产生的反Lambda粒子的极化

We study the polarization of produced Λ in s=200GeV polarized proton-proton collision at RHIC/PHENIX, and also the polarization as a function of its rapidity which may be sensitivity to the quark helicity distributions of the proton and to the polarized fragmentation functions of the quark into the baryon. For polarized data collected in 2003 a very clean Λ peak in pπ⁺ invariant mass spectrum in the mid-rapidity(|η|<0.35) is obtained. In this letter, we report the calculation process of P_Λ as extracted from the data.