Speaker
Description
The study of the origins of transverse single-spin asymmetries has stimulated significant progress in the development of twist-3 formalism and transverse-momentum-dependent parton distribution functions (TMDs). Measurements of the azimuthal distribution of inclusive jets and identified hadrons within jets produced in transversely polarized hadronic interactions provide key insights into TMD physics. In particular, measurements of the Collins effect, which involves the interplay between the quark transversity and Collins fragmentation function, provide access to the final-state phenomena of TMD physics. This talk will report measurements of transverse single-spin asymmetries for inclusive jets and hadrons within jets, obtained in recent years at RHIC-STAR. In particular, the polarized $pp$ collision dataset taken in 2017, with an integrated luminosity of 320 $\mathrm{pb}^{-1}$, has significantly improved the precision of these measurements. The comparison of Collins asymmetries between ${pp}$ collisions at 200 GeV and 510 GeV can provide crucial insights into the TMD evolution of the Collins function. Additionally, comparing experimental results from ${pp}$ collisions with theoretical predictions derived from global fits to semi-inclusive deep inelastic scattering and $e^+e^-$ annihilation data will allow tests of the universality of Collins effect.
