18-22 October 2021
Matsue, Shimane Prefecture, Japan
Asia/Tokyo timezone

Measurement of longitudinal spin transfer of the $\Lambda(\bar{\Lambda})$ hyperon in longitudinally polarized $\rm{p}$$+$$\rm{p}$ collisions at $\sqrt{s}=200$ $\rm{GeV}$ at RHIC-STAR

20 Oct 2021, 11:45
Room 501 (Kunibiki Messe)

Room 501

Kunibiki Messe

Parallel Session Presentation Nucleon Helicity Structure Nucleon Helicity Structure


Yi Yu (Shandong University)


Since the first surprising results on the spin structure of the proton by the EMC experiment in the late 1980s, much progress has been made in understanding the origin of the proton spin. However, the sea quark contribution to the proton spin, for example, the helicity distributions of the strange quark (anti-quark), $s(\bar{s})$, is still not well constrained by experimental data. Since the $s(\bar{s})$ is expected to carry a substantial fraction of the spin of the $\Lambda(\bar{\Lambda})$ hyperon, measurements of the longitudinal spin transfer, $D_{LL}$, of the $\Lambda(\bar{\Lambda}$) hyperon can thus shed light on the helicity distribution of the $s(\bar{s})$ and the longitudinally polarized fragmentation functions. In this talk, we will present the status of the $\Lambda(\bar{\Lambda}$) $D_{LL}$ analysis using data collected at RHIC-STAR in 2015, for the pseudo-rapidity $|\eta| < 1.2$ and transverse momenta up to $8.0$ $\rm{GeV}$$/c$. The $D_{LL}$ as a function of the longitudinal momentum fraction of the $\Lambda(\bar{\Lambda})$ hyperon in the jet is also investigated. This data set is about twice as large as the 2009 data used for the previously published $D_{LL}$ results.In addition, the longitudinal double spin asymmetries, $A_{LL}$, of the $\Lambda(\bar{\Lambda})$ hyperon and the $K_{S}^{0}$ meson are investigated, which are also expected to be sensitive to the $s(\bar{s})$ helicity distributions.

Primary author

Yi Yu (Shandong University)

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