Measurement of Transverse Spin Dependent Azimuthal Correlations of Charged Pion(s) in $p^{\uparrow} p$ Collisions at $\sqrt s = 200$ GeV at STAR

TL;DR

This paper reports the measurement of azimuthal correlations of charged pions in transversely polarized proton-proton collisions, providing insights into the nucleon's transverse spin structure via the transversity distribution function.

Contribution

It presents the first measurement of transverse spin-dependent azimuthal correlations of charged pions in $p^{rrow} p$ collisions at $ oot s = 200$ GeV, probing the transversity distribution.

Findings

Observed non-zero azimuthal asymmetries in charged pion correlations.

Provides experimental data to constrain transversity distribution functions.

Enhances understanding of nucleon transverse spin structure.

Abstract

At the leading twist, the transversity distribution function, $h^{q}_{1}(x)$, where $x$ is the longitudinal momentum fraction of the proton carried by quark $q$, encodes the transverse spin structure of the nucleon. Extraction of it is difficult because of its chiral-odd nature. In transversely polarized proton-proton collisions ($p^\uparrow p$), $h_{1}^{q}(x)$ can be coupled with another chiral-odd partner, a spin-dependent fragmentation function (FF). The resulting asymmetries in hadron(s) azimuthal correlations directly probe $h_{1}^{q}(x)$. We report the measurement of correlation asymmetries for charged pion(s) in $p^\uparrow p$, through the Collins and the Interference FF channel.