Correlations of dihadron polarization in central, peripheral and ultraperipheral heavy-ion collisions

TL;DR

This paper investigates dihadron polarization correlations in heavy-ion collisions, revealing potential for new insights into spin transfer mechanisms and fragmentation functions, especially in central collisions and ultraperipheral events.

Contribution

It extends the study of dihadron polarization correlations to relativistic heavy-ion collisions, incorporating energy loss effects in the quark-gluon plasma and exploring their sensitivity to fragmentation function models.

Findings

Enhanced polarization correlations in central collisions.

Sensitivity of correlations to fragmentation function parameterizations.

Potential for constraining spin-dependent fragmentation functions.

Abstract

While jet quenching in relativistic heavy-ion collisions has been extensively studied over decades, the polarization of quenched hadrons has rarely been discussed. It has recently been proposed that the correlations of dihadron polarization in $e^+e^-$ and $pp$ collisions provide a novel probe of the longitudinal spin transfer from hard partons to hadrons without requiring the colliding beams to be polarized. To support realistic experimental measurement of dihadron polarization with sufficient luminosity, we extend the aforementioned study to relativistic heavy-ion collisions by convoluting the vacuum fragmentation of partons with their energy loss inside the quark-gluon plasma (QGP). We find that while the correlation functions of $\Lambda$-$\Lambda$ (or $\Lambda$-$\bar{\Lambda}$) polarization in peripheral collisions is consistent with those in $pp$ collisions, clear enhancement can be seen in central collisions. These correlation functions appear sensitive to different assumptions in the DSV parameterization of parton fragmentation functions, and therefore could place additional constraints on the spin-dependent fragmentation functions of quarks and gluons. The correlation of dihadron polarization has also been explored in ultraperipheral heavy-ion collisions, which provides a cleaner probe of fragmentation functions of quarks produced by energetic photon-photon and photon-pomeron interactions.