Transverse Spin Dependent Azimuthal Correlations of Charged Pion Pairs in $p^{\uparrow}p$ collisions at $\sqrt{s} = 510$ GeV at STAR

The transversity distribution $h^q_1(x)$ describes transversely polarized quarks inside a transversely polarized nucleon. As $h^q_1(x)$ is chiral-odd, it can only be accessed via a process where it couples to another chiral-odd function, such as the spin-dependent interference fragmentation function (IFF) in $p^\uparrow p$ collisions. The coupling of $h^q_1(x)$ and IFF yields an experimentally measurable di-hadron correlation asymmetry, $A_{UT}$. To access $h^q_1(x)$ at high $Q^2$, where QCD framework is well understood, precise measurement of $A_{UT}$ at high center-of-mass energy, $\sqrt s$, is crucial. Previously, the STAR experiment at RHIC measured non-zero $A_{UT}$ using $p^\uparrow p$ data from 2011 at $\sqrt s= 500$ GeV with an integrated luminosity of $25$ pb$^{-1}$. In 2017, STAR collected $\sim 350$ pb$^{-1}$ of $p^\uparrow p$ data at $\sqrt s=510$ GeV which will significantly improve the statistical precision of $A_{UT}$ measurement and thus further constrain global fits of $h^q_1(x)$, especially for $0.07