# The 24th International Spin Symposium

18-22 October 2021
Matsue, Shimane Prefecture, Japan
Asia/Tokyo timezone

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

21 Oct 2021, 09:16
18m
Room 601 (Kunibiki Messe)

### Room 601

#### Kunibiki Messe

Parallel Session Presentation Transverse momentum structure (TMD)

### Speaker

Babu Pokhrel (Temple University)

### Description

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 proton. Extraction of it is difficult because of its chiral-odd nature. However, it can be coupled to a spin-dependent interference fragmentation function, leading to experimentally measurable azimuthal correlations, $A_{UT}$, between the spin of the fragmenting quark and oppositely charged final state hadron pairs (di-hadron). The STAR experiment at RHIC has previously observed non-zero $A_{UT}$ for $\pi^+\pi^-$ pairs using $p^\uparrow p$ collision data at $\sqrt{s} = 200$ GeV from 2006 and at $\sqrt{s}= 500 \ \mathrm{GeV}$ from 2011, corresponding to integrated luminosities, $L$, of $1.8\ \mathrm{pb^{-1}}$ and $25\ \mathrm{pb^{-1}}$, respectively. In 2015, STAR collected $L\sim 52\ \mathrm{pb^{-1}}$ of $p^{\uparrow}p$ collisions at $\sqrt{s}=200$ GeV. This dataset provides highest precision $A_{UT}$ measurement at $\sqrt{s}=200$ GeV to date, which covers quark momentum fractions $0.1< x< 0.4$, and is sensitive to valence quark $h_{1}^{q}(x)$. We will present preliminary results on $A_{UT}$ for $\pi^+\pi^-$pairs based on this dataset.

### Primary author

Babu Pokhrel (Temple University)