Speaker
Description
Transversity, $h_1^{q}(x)$, a leading twist parton distribution function, describes the transverse spin distribution of quarks in a transversely polarized proton. It is a fundamental component of nucleon spin structure and is loosely constrained by global fits. As a chiral odd function, $h_1^{q}(x)$ can only be accessed when coupled with another chiral odd partner, such as an interference fragmentation function (IFF). This coupling of $h_1^{q}(x)$ and IFF leads to a measurable azimuthal correlation asymmetry ($A_{UT}$) of hadron pairs in final states. The STAR experiment at RHIC has previously reported non-zero $A_{UT}$ for $\pi^+\pi^-$ in transversely polarized proton-proton ($p^\uparrow p$) collisions at $\sqrt{s} $ = 200, 500, and 510 GeV. Measurements of di-hadron $A_{UT}$ with other hadron species provide additional flavor sensitivity, for example, measurements with $K^+K^-$ provide access to $h_1^{q}(x)$ of strange quarks. While non-zero $A_{UT}$ has been measured for $\pi^{+}\pi^{-}$ pairs, we will present an update on the ongoing analysis of $A_{UT}$ for identified hadron pairs using the 2015 $p^{\uparrow}p$ data at $\sqrt{s} = 200$ GeV in the mid-pseudorapidity region $(|\eta|<1)$, focusing on $K^{+}K^{-}$, $K^{+}\pi^{-}$, and $\pi^{+}K^{-}$ pairs.
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