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

Measurement of transverse single-spin asymmetries for dijet production in polarized p+p collisions at \sqrt{s} = 200 GeV at STAR

22 Oct 2021, 07:00
18m
Room 601 (Kunibiki Messe)

Room 601

Kunibiki Messe

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

Speakers

Prof. Scott Wissink (Indiana University) The STAR Collaboration

Description

We report a new measurement of transverse single-spin asymmetries for pair-production of jets in collisions of transversely polarized protons at $\sqrt{s}$ = 200 GeV with data taken in 2012 and 2015 at STAR. In this measurement we probe, at high $Q^2$, correlations between the transverse spin ($\vec S$) of a proton, moving in the longitudinal ($\vec p$) direction, and the transverse momenta of partons ($\vec k_T$) within the proton. A non-zero correlation -- the Sivers effect -- results in a spin-dependent shift in the dijet azimuthal opening angle away from 180$^\circ$. The corresponding $\langle k_T \rangle$ is then calculated based on a simple kinematic model. By using charge-tagging of the jets to enhance either $u$- or $d$-quark contributions, we see a non-zero Sivers effect for the first time in dijet production in high-energy proton collisions. The individual parton contributions ($u$, $d$, gluon+sea) to the measured $\langle k_T \rangle$ are extracted through a matrix inversion of the charge-sorted $\langle k_T \rangle$ data. Preliminary results and status of the analysis will be presented.

Primary author

Prof. Scott Wissink (Indiana University)

Presentation Materials

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