How quarks and gluons conspire to provide the total spin of proton is a long-standing puzzle in quantum chromodynamics (QCD). The unique capability of RHIC, that can provide longitudinally polarized $p+p$ collisions at both $\sqrt{s} = 200$ GeV and $\sqrt{s} = 510$ GeV, opened new territory to constrain the helicity structure of the proton with unprecedented depth and precision.
Results from various STAR spin measurements have contributed significantly to our understanding of the quark and gluon helicity distributions inside the proton. The longitudinal double-spin asymmetry, $A_{LL}$, from the STAR 2009 inclusive jet measurement, provides the first indication of the positive gluon polarization with partonic momentum fraction $x$ greater than 0.05 inside the proton. More precise measurements using the $p+p$ data collected in 2012, 2013 and 2015 at both $\sqrt{s}$ = 510 and 200 GeV confirm the previous findings and provide additional constraints in the largely unexplored region of $x < 0.05$. Compared to the inclusive jet observables, analyses of dijet production extending to higher pseudorapidity (up to $η\sim 1.8$) provide better constraints on the $x$ dependent behavior of $Δg(x)$. Moreover, the reconstruction of $W^{\pm}$ in longitudinally polarized proton-proton collisions provides significant constraints on the flavor separation of the light sea quark helicity distributions inside the proton, while the longitudinal spin transfer to $Λ$ and $\bar Λ$ hyperons provides access to the helicity of strange and anti-strange quarks in the proton.
In this proceeding, an overview of dijet measurements from longitudinally polarized proton-proton collisions at STAR is presented.
Inclusive cross section and double helicity asymmetry for π^0 production in p+p collisions at sqrt(s)=200 GeV: Implications for the polarized gluon distribution in the proton
The gluon spin contribution to the proton spin from the double helicity asymmetry in inclusive pi^0 production in polarized p+p collisions at sqrt(s)=200 GeV
Towards constraining triple gluon operators through tops
有效场论技术为我们以相对独立于模型的方式探索超越标准模型的物理提供了重要的工具。在这项工作中，我们重新CP-偶数维-6纯胶子运营商调查可能的限制，通过研究它的顶部对生产的LHC，特别是高$p_T$和$m_{t\bar{t}}$尾部的分布的影响。基于切割的分析表明，当这个操作员单独对生产过程做出贡献时，新物理学的规模在95% C. L.时大于3.4 TeV，这是一个强得多的界限相比，850 GeV的界限，从运行-I数据使用相同的通道。这一点通过使用机器学习技术的分析得到了加强。我们的研究补充了类似的研究，集中在其他对撞机通道，以研究该运营商。
Two-gluon exchange contribution to elastic $γγ\to γγ$ scattering and production of two-photons in ultraperipheral ultrarelativistic heavy ion and proton-proton collisions
在高能近似下讨论了双胶子交换（形式上为三环）对弹性光子-光子散射的贡献。弹性$γγ\to γγ$振幅在所有螺旋度组态和有限夸克质量的冲击因子表示中给出。我们讨论的重要性，包括魅夸克，其中的贡献，由于干扰，可以大大提高截面。我们研究了软区对$γγ\to γγ$振幅的贡献，通过研究它对非微扰胶子质量的依赖。螺旋翻转的贡献被证明是远远小于螺旋守恒的。我们确定区域（S）的相空间中的两个胶子交换的贡献成为重要的成分相比，箱和非微扰的VDM-Regge机制在文献中考虑。讨论了$A A \to A A γγ$反应的后果。显示了几个微分分布。本文对双胶子交换效应进行了可行性研究。我们对$p p \to p p γγ$反应进行类似的分析。只有对$M_{γγ}$进行严格的削减，并对光子横动量进行窄窗处理，双胶子贡献才能与盒子贡献相媲美，但相应的截面相当小。
Helicity Dependent Distribution Functions of the Proton and $Λ$ and $Σ^0$ Baryons
East China Jiaotong University（华东交通大学）；Anhui Normal University（安徽师范大学）；Nanjing University（南京大学）；European Centre for Theoretical Studies in Nuclear Physics and Related Areas（核物理及相关领域欧洲理论研究中心）
