Transverse spin transfer to $\Lambda$ and $\bar{\Lambda}$ hyperons in polarized proton-proton collisions at $\sqrt{s}=200\,\mathrm{GeV}$

TL;DR

This paper reports the first measurement of transverse spin transfer to $ ext{Lambda}$ and $ar{ ext{Lambda}}$ hyperons in transversely polarized proton-proton collisions at 200 GeV, providing insights into nucleon transversity and fragmentation functions.

Contribution

It presents the first experimental measurement of the transverse spin transfer $D_{TT}$ in polarized proton collisions, testing theoretical models and expanding understanding of spin transfer mechanisms.

Findings

$D_{TT}$ results are consistent with zero within uncertainties.

Data are compatible with model predictions.

Results cover $p_T$ up to 8 GeV/c and $| ext{eta}|<1.2$.

Abstract

The transverse spin transfer from polarized protons to $\Lambda$ and $\bar{\Lambda}$ hyperons is expected to provide sensitivity to the transversity distribution of the nucleon and to the transversely polarized fragmentation functions. We report the first measurement of the transverse spin transfer to $\Lambda$ and $\bar{\Lambda}$ along the polarization direction of the fragmenting quark, $D_\mathrm{TT}$, in transversely polarized proton-proton collisions at $\sqrt{s}=200\,\mathrm{GeV}$ with the STAR detector at RHIC. The data correspond to an integrated luminosity of $18\,\mathrm{pb}^{-1}$ and cover the pseudorapidity range $\left|\eta\right| < 1.2$ and transverse momenta $p_{\mathrm{T}}$ up to $8\,\mathrm{GeV}/c$. The dependence on $p_\mathrm{T}$ and $\eta$ are presented. The $D_\mathrm{TT}$ results are found to be comparable with a model prediction, and are also consistent with zero within uncertainties.