论文标题
使用两极分化的$ pp $ Collisions探索夸克横向和柯林斯碎片函数
Exploring the Quark Transversity and the Collins Fragmentation Functions using Polarized $pp$ Collisions at STAR
论文作者
论文摘要
在强相互作用物理学中，了解核子的内部自旋结构仍然是一个挑战。横向性描述了横向极化质子中夸克的横向自旋结构，受到实验数据的约束很差。由于它是手性odd，因此只能通过将夫妇与其他手性-ODD分布（例如Collins碎片函数（所谓的Collins效应）或干扰碎片函数）访问。最近，使用软共线有效理论进行了详细的计算，发现$ PP $碰撞中的柯林斯效应涉及共线和横向动量依赖性（TMD）分解的混合物。 Collins效应提供了对Collins碎片函数的直接探针，并可以测试其进化，普遍性和分解分解在横向动量依赖性形式主义中。 In 2018, STAR published the first measurements of Collins asymmetries for charged pions in jets in polarized $pp$ collisions at $\sqrt{s}$ = 500 GeV based on data taken during 2011. These measurements probe $Q^2$ scales one to two orders of magnitude larger than similar measurements in semi-inclusive deep-inelastic scattering (SIDIS) and the results are consistent with predictions based on $ e^{+} e^{ - } $和SIDIS数据的全局分析。在2012年和2015年，STAR收集的$ \ sim $ 14 $ \ MATHRM {pb^{ - 1}} $和$ \ sim $ 52 $ \ MATHRM {pb^{ - 1}} $分别分别偏置的$ PP $数据分别为$ \ sqrt {s} $ = 200 GEV，分别为$ \ sqrt {s} $ = 200 geev。这些数据集提供了迄今为止200 GEV $ PP $碰撞中Collins效应的最精确测量，尤其是在Quark Mompartions $ 0.1 \ le x \ le 0.4 $的情况下。这些程序介绍了$ \ sqrt {s} $ = 200 GEV和与理论预测的比较，$ pp $ collisions in $ pp $ collisions in $ pp $ collisions in $ pp $ collisions中识别的乳头的初步结果。
Understanding the internal spin structure of the nucleon still remains a challenge in strong interaction physics. Transversity, which describes the transverse spin structure of quarks in a transversely polarized proton, is poorly constrained by experimental data. Since it is chiral-odd, it can only be accessed through channels that couple to other chiral-odd distributions, like the Collins fragmentation functions (so-called Collins effect) or the interference fragmentation functions. Recently, a detailed calculation using the soft-collinear effective theory found that the Collins effect in $pp$ collisions involves a mixture of collinear and transverse momentum dependent (TMD) factorization. The Collins effect provides a direct probe to the Collins fragmentation function and enables testing of its evolution, universality and factorization breaking in the transverse momentum dependent formalism. In 2018, STAR published the first measurements of Collins asymmetries for charged pions in jets in polarized $pp$ collisions at $\sqrt{s}$ = 500 GeV based on data taken during 2011. These measurements probe $Q^2$ scales one to two orders of magnitude larger than similar measurements in semi-inclusive deep-inelastic scattering (SIDIS) and the results are consistent with predictions based on global analyses of $e^{+}e^{-}$ and SIDIS data. In 2012 and 2015, STAR collected $\sim$14 $\mathrm{pb^{-1}}$ and $\sim$52 $\mathrm{pb^{-1}}$ of transversely polarized $pp$ data at $\sqrt{s}$ = 200 GeV, respectively. These datasets provide the most precise measurement of the Collins effect in 200 GeV $pp$ collisions to date, especially at the quark momentum fractions $0.1 \le x \le 0.4$. These proceedings present the preliminary results for Collins asymmetries of identified pions in jets in $pp$ collisions at $\sqrt{s}$ = 200 GeV and comparisons to theory predictions.
