Nuclear Physics Seminar

"Recent STAR spin Results II"

Presented by Ting Lin and Huanzhao Liu

Tuesday, June 30, 2020, 11:00 am — Webcast

This will consist of two talks. First talk by: Ting Lin, Cyclotron Institute, Texas A&M University Title: "Azimuthal Transverse Single-Spin Asymmetries of Charged Pions Within Jets from Polarized pp Collisions at sqrt(s) = 200 GeV" Abstract: Collins effect involves convolution of the quark transversity in the proton with the spin-dependent Collins fragmentation function, leading to azimuthal modulations of identified charged hadron yields about the jet axis. We report new preliminary results for the Collins asymmetry from 2015 proton+proton collisions at sqrt(s) = 200 GeV, which probe higher momentum scales (Q2 ~ 170 GeV2) than the measurements from semi-inclusive deep inelastic scattering (Q2 < 20 GeV2) and enable the test of the evolution, universality and factorization breaking in the transverse momentum dependent (TMD) formalisms. Second talk by: Huanzhao Liu, Indiana University, Center for Exploration of Energy and Matter Title: "Measurement of transverse single-spin asymmetries for di-jet production in polarized p+p collisions at sqrt(s) = 200 GeV at STAR" Abstract: We report a new measurement of the transverse single-spin asymmetries for pair-production of jets in collisions of transversely polarized protons at sqrt(s) = 200 GeV at STAR, with data taken in 2012 and 2015. The correlation between the transverse momentum of a parton (k_T) and the transverse spin (S) of its proton, moving in the longitudinal (p) direction, is probed in the measurement, together with an estimate of the corresponding Sivers calculated based on a simple kinematic model. By employing flavor-tagging to separate u- and d-quarks, we see non-zero Sivers effects for the first time in di-jet production in transversely polarized proton collisions.

Hosted by: Salvatore Fazio

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