25th International Spin Symposium (SPIN 2023)

Measurements of Transverse Spin Dependent π+π− Azimuthal Correlation Asymmetry and Unpolarized π+π− Cross Section in pp Collisions at s=200 GeV at STAR

Sep 25, 2023, 2:25 PM

15m

Meeting Room 1-2 (Durham Convention Center)

Talk 3D Structure of the Nucleon: TMDs 3D Structure of the Nucleon: TMDs

Speaker

Babu Pokhrel (Temple University)

Description

The transversity distribution function, $h_1^q(x)$, encapsulates the transverse spin structure of the proton at the leading twist, where $x$ represents the longitudinal momentum fraction carried by the quark $q$. The extraction of $h_1^q(x)$ poses a formidable challenge due to its chiral-odd nature. Measurements of final-state di-hadron pairs in transversely polarized proton-proton ($p^{\uparrow }p$) collisions directly probe the collinear quark transversity via coupling with a chiral-odd interference fragmentation function, $H_1^{\sphericalangle ,q}$. This coupling results in an experimentally measurable azimuthal correlation asymmetry, $A_{UT}$. The asymmetry originates from the interplay between the spin orientation of the fragmenting quark and the resulting di-hadron in the final state. Thus, it necessitates precise knowledge of unpolarized di-hadron fragmentation functions (FFs) to achieve a model-independent extraction of the transversity from these measurements. These FFs can be obtained by measuring the unpolarized di-hadron cross section in $pp$ collisions. We will present preliminary results on the $A_{UT}$ for ${\pi }^{+}{\pi }^{-}$ pairs using $p^{\uparrow }p$ data collected by the STAR experiment at a center-of-mass energy of $\sqrt{s}=200$ GeV in 2015. Additionally, we will present preliminary results of the unpolarized ${\pi }^{+}{\pi }^{-}$ cross section using $pp$ data at $\sqrt{s}=200$ GeV collected in 2012.

Presentation materials

Babu_XsecIFF_SPIN2023.pdf