Hyperon Polarization in Unpolarized Scattering Processes

TL;DR

This paper investigates transverse Lambda polarization in unpolarized SIDIS and hadronic $pp$ scattering using twist-three quark-gluon-antiquark correlations, focusing on the distribution $T_F^{(\sigma)}(x_1,x_2)$ and its coupling to the transversity fragmentation function $H_{1T}$. It demonstrates that in the intermediate transverse momentum regime $\Lambda_{QCD} \ll P_{\Lambda\perp} \ll Q$, the twist-three approach and the TMD factorization yield a unified description, including a perturbative tail for the Boer-Mulders function $h_{1,DIS}^{\perp}$ that matches the TMD picture with $H_{1T}$. In $pp$ collisions, the calculation reveals that only derivative contributions survive for Lambda polarization, with non-derivative terms vanishing, challenging some compact twist-three formulations. The study links collinear and TMD frameworks and yields insights into process-dependent Boer-Mulders effects and potential Drell-Yan manifestations, thereby advancing the understanding of hyperon polarization in high-energy hadronic processes.

Abstract

Transverse polarization in the Hyperon production in the unpolarized deep inelastic scattering and pp collisions is studied in the twist-three approach, considering the contribution from the quark-gluon-antiquark correlation distribution in nucleon. We further compare our results for deep inelastic scattering to a transverse momentum dependent factorization approach, and find consistency between the two approaches in the intermediate transverse momentum region. We also find that in pp collisions, there are only derivative terms contributions, and the non-derivative terms vanish.

Figures (1)

• Figure 1: The example diagrams for the soft pole (a) and hard pole (b) contributions to $\Lambda$ transverse polarization in semi-inclusive DIS process. The short bars indicate the pole contribution from the propagators.