Speaker
Dr
Zilong Chang
(Brookhaven National Laboratory)
Description
Talk title: Spin Physics at the STAR experiment
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Speaker: Dr. Zilong Chang, Brookhaven National Lab
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Abstract:
The proton structure has been studied extensively over the past a few decades, especially from the polarized Deep Inelastic Scattering (DIS) Experiments. However due to its limit coverage in $𝑥−𝑄^2$ phase space and inability to directly access gluon inside the proton, at Relativistic Heavy Ion Collider (RHIC), the world-only polarized proton collider, it provides excellent opportunities to study the internal structure of proton. At both √𝑠=200 and 510 GeV, the Solenoidal Tracker at RHIC (STAR) experiment has carried out a series of measurements from both longitudinally and transversely polarized 𝑝𝑝 collisions. The longitudinal double spin asymmetry, $𝐴_{𝐿𝐿}$ from inclusive jet and dijet production at √𝑠=200 GeV provided the first evidence of the positive gluon polarization for 𝑥>0.05. At √𝑠=510 GeV, the same measurements have pushed the gluon polarization down to 𝑥∼0.02. The longitudinal single-spin asymmetry $𝐴_𝐿$ from $𝑊^±$ boson at √𝑠=510 GeV shows that 𝑢-flavor sea quark polarization, $∆\overline{𝑢}$, is larger than the 𝑑-flavor sea quark polarization, $∆\overline{𝑑}$. The transverse single-spin dependence of the azimuthal asymmetry of charged pions in a jet indicated the first evidence of transversity in the 𝑝𝑝 collisions. The results enable to test the universality and factorization-breaking effects in 𝑝𝑝 collisions for Transverse-Momentum Dependent (TMD) distributions. In this talk, I will present the published and current measurements from STAR that explore both the helicity distribution functions and transverse structure of the proton.
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Self-introduction:
Zilong Chang got his B.S. in Physics from University of Science and Technology of China in 2010, and his Ph.D in Physics from Texas A&M University in 2016. Since 2017, he has been working at Brookhaven National Laboratory as a post-doc researcher. His doctoral dissertation is on measurements of longitudinal double-spin asymmetry for inclusive jet production from √𝑠 = 510 GeV polarized 𝑝𝑝 collisions at STAR. Currently he is working with the same dataset to extract the inclusive jet cross-section to explore the gluon parton distribution function inside the proton.
