Antihyperon polarization in high energyppcollisions with polarized beams

Abstract

We study the longitudinal polarization of theΣ − ,Σ + ,Ξ 0 andΞ + anti-hyperons in polarized high energy pp collisions at large transverse momenta, extending a recent study for theΛ anti-hyperon.We make predictions by using different parameterizations of the polarized parton densities and models for the polarized fragmentation functions. Similar to theΛ polarization, theΞ 0 andΞ + polarizations are found to be sensitive to the polarized anti-strange sea, ∆s(x), in the nucleon. Thē Σ − andΣ + polarizations show sensitivity to the light sea quark polarizations, ∆ū(x) and ∆d(x), and their asymmetry.

Nucleon spin structure and measurements on sea quark polarization at RHIC

“…以Λ超子为例, 在极化的 pp反应中, 产生的末态Λ超子的纵向极化也称作纵向 自旋转移, 用D LL 表示, 定义为 [10] . 而其 他不同超子如Σ和Ξ及其反粒子的极化, 对不同味道海 夸克极化的依赖各不相同 [11] . 实验上对pp反应中各类 超子与反超子极化的系统测量将为核子内奇异海夸克 自旋分布的研究提供一个新的方法.…”

“…Results of longitudinal spin transfer for anti-hyperons in polarized pp collisions. Plot is from ref [11]…”

Longitudinal and transverse spin transfer to $\Lambda$ and $\bar \Lambda$ hyperons in $p+p$ collisions at STAR

“…In particular, the transverse spin transfer to Λ (Λ) in hadron-hadron collisions provides a natural connection to transversity of (anti-)strange quarks through polarized fragmentation functions [1,2,3]. Similarily, the longitudinal spin transfer to Λ (Λ) hyperons in hadron-hadron collisions provides sensitivity to the helicity distribution of (anti-)strange quarks [3,4,5,6,7,8].…”

Nucleon strangeness polarization from $$\varLambda /\bar{\varLambda }$$ hyperon production in polarized proton–proton collision at RHIC

“…However, the understanding of helicity distributions for strange-antistrange quark pairs Δs(x) and Δs(x) is far from satisfactory and needs further studies. Researches show that studies of spin-transfer a e-mail: mabq@pku.edu.cn reactions [30][31][32][33][34][35][36][37][38][39][40][41][42] and measurements of the polarized structure function [1,2,[43][44][45][46][47][48], can provide new insights into the nucleon spin structure and yield a better understanding of the hadronization process. The Λ baryon plays a special role in this respect since it has a rather simple spin structure in the naive quark parton model [49], as well as that its self-analyzing parity violating decays [50] make polarization measurements experimentally feasible.…”

“…The STAR experiment at Relativistic Heavy Ion Collider (RHlC) [51][52][53] is carrying out a spin physics program in high-energy polarized proton-proton collisions at √ s = 200 GeV and √ s = 500 GeV in order to gain a deeper insight into the nucleon spin structure and dynamics of the proton. Theoretical investigations [33,35,36,[38][39][40][41][42] suggest that the spin transfer process of the Λ/Λ production in the singly polarized proton-proton collision provides a platform to extract polarized parton distribution functions of the proton and polarized quark fragmentation functions of quarks into Λ/Λ hyperon. The experiments measuring the polarization of Λ hyperon produced in singly polarized pp collisions [54,55] may provide information about not only the inclusive production of hadrons but also the strange and antistrange quark polarizations inside the proton.…”