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
Room 601 (Kunibiki Messe)

Room 601

Kunibiki Messe

Parallel Session Presentation Transverse momentum structure (TMD) Transverse Momentum Structure (TMD)


Babu Pokhrel (Temple University)


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)

Presentation Materials