Speaker
Description
The trasverse polarization of quarks within a trasversely polarized nucleon, $h^q_1(x)$, can only be accessed through processes involving its coupling with another chiral-odd functions, such as the spin-dependent interference fragmentation function (IFF) in polarized proton-proton collisions. The coupling of $h^q_1(x)$ and IFF leads to a measurable azimuthal correlation asymmetry ($A_{UT}$) of di-hadron pairs in the final state. In previous work, the STAR experiment at RHIC measured a non-zero $A_{UT}$ using polarized proton-proton ($p^\uparrow p$) data from 2011 at $\sqrt s = 500$ GeV, with an integrated luminosity of 25 pb$^{-1}$. The precise measuremnt of $A_{UT}$ together with unpolarized di-hadron cross section will help to constrain the $h^q_1(x)$ in the global fits. In 2017, the STAR experiment collected dataset of approximately 350 pb$^{-1}$ from $p^\uparrow p$ collisions at $\sqrt s = 510$ GeV. In 2022, another dataset featuring $p^\uparrow p$ collisions at $\sqrt s = 508$ GeV of an integrated luminosity of approximately 400 pb$^{-1}$ was collected. These new datasets will significantly improve the statistical precision of the $A_{UT}$ measurement. In this talk, we will present an update on the measurement of $A_{UT}$ for pion pairs in the pseudorapidity region $|\eta|<1$ based on the 2017 $p^\uparrow p$ dataset and the projection for the 2022 dataset.
