Predictions for the spin dependent structure function $g_1$ of the nucleon are presented. We use an unified approach incorporating the LO DGLAP evolution and the resummation of double logarithmic terms $ln^2(x)$. We show, that the singular input parametrisation as $x\to 0$ can be a substitute of the $ln^2(x)$ resummation. An impact of the `more running' coupling is discussed. We determine the contribution to the Bjorken sum rule solving the evolution equation for the truncated moment of $g_1^{NS}$. A comparison with the re-analysed HERMES and COMPASS data is given.
We have presented the results for the single and double spin asymmetries in semi-inclusive deep inelastic scatterings for proton in a light front quark-diquark model. The asymmetries generated by the T-even TMDs are discussed here. The model predictions are found to agree with the available data. We also present our model predictions for the Collins asymmetry for the future electron-ion collider experiments.
Experimental data for integrated kaon multiplicities taken at HERMES and COMPASS measurements look incompatible with each other. In this talk, we investigate the effects of hadron masses calculated at leading-order and leading twist at the kinematics of these two experiments. We present evidence that Hadron Mass Corrections can fully reconcile the data for the $K^+/K^-$ multiplicity ratio, and can also sizeably reduce the apparent large discrepancy in the case of $K^+ + K^-$ data. Residual differences in the shape of the latter one remains to be understood.
In this paper we study the Kotzinian-Mulders effect of a single hadron production in semi-inclusive deep inelastic scattering (SIDIS) within the framework of transverse momentum dependent (TMD) factorization. The asymmetry is contributed by the convolution of the Kotzinian-Mulders function $g_{1T}$ and the unpolarized fragmentation function $D_1$. As a TMD distribution, the Kotzinian-Mulders function in the coordinate space in the perturbative region can be represented as the convolution of the $C$-coefficients and the corresponding collinear correlation function. The Wandzura-Wilczek approxim…
测量轻子和核子的深度非弹性散射（DIS），$e+p\to e+X$，可以提取部分子分布函数（PDF），它描述了组成快速运动核子的夸克、反夸克和胶子所携带的纵向动量。虽然PDF为涉及强子的微扰量子色动力学（QCD）计算提供了重要的输入，但它们并没有提供核子部分子结构的完整图像。特别是，PDF既不包含关于部分子之间的相关性的信息，也不包含关于它们的横向运动的信息。近年来，核子保持完整的硬排他过程已经成为补充这一基本一维图像的主要候选者。最简单的排斥过程是深虚康普顿散射（DVCS）或排斥产生实光子$e + p \to e + γ+ p$。这个过程是特别感兴趣的，因为它既有一个明确的实验签名，是可计算的微扰QCD。DVCS反应可以被看作是虚光子通过无色交换从质子上弹性散射，产生最终状态的实光子。在Bjorken标度体系中，QCD计算假设交换涉及两个部分子，具有不同的纵向和横向动量，在无色的配置。这些不相等的动量或偏斜是入射虚光子和出射实光子之间质量差的结果。这种偏态效应可以在广义部分子分布（GPD）的背景下解释。在这一过程中，我们研究了HERA的典型测量和CERN的COMPASS的前景，这可以为核子的夸克/胶子成像带来新的见解。
Threshold Resummation for Polarized High-$p_T$ Hadron Production at COMPASS
本文研究了入射光子和核子纵向极化的光生过程$γN\rightarrow h X$的截面，在高横动量下观察到一个强子$h$。具体来说，我们解决的“直接”的截面的一部分，光子相互作用的点状方式。对于这方面的贡献，我们进行了一个所有的顺序recremation的对数阈值修正所产生的软或共线胶子发射到下一个领先的对数精度。我们目前的现象学结果相关的COMPASS实验和比较最近的COMPASS数据。
Preliminary results obtained by the COMPASS experiment for longitudinal-spin-dependent azimuthal asymmetries in single-hadron muoproduction off protons are presented for the first time. The analysis was carried out on the full data sample collected by COMPASS with longitudinally polarized proton ($NH_3$) target in 2007 and 2011 using 160~\gvc and 200~\gvc muon beams, correspondingly. Within QCD parton model approach extracted asymmetries are giving access to the specific convolutions of certain transverse-momentum-dependent \textit{twist-2} and \textit{higher twist} parton distribution functio…
We present generalized evolution equations and factorization in terms of the truncated Mellin moments (TMM) of the parton distributions and structure functions. We illustrate the $x$ and $Q^2$ dependence of TMM in the polarized case. Using the TMM approach we compare the integrals of $g_1$ with HERMES and COMPASS data from the limited $x$-ranges.
We complete our earlier study of the "direct" part of the cross section and spin asymmetry for the photoproduction process $γN\rightarrow h X$ by analysing the "resolved" contribution, for which the photon couples like a hadron through its parton structure. The incident photon and nucleon are longitudinally polarized and one observes a hadron $h$ at high transverse momentum $p_T$. Soft or collinear gluon emissions generate large logarithmic threshold corrections which we resum to next-to-leading logarithmic order. We compare our results with recent spin asymmetry data by the COMPASS collaborat…
We present model predictions of Collins asymmetries for proton in the SIDIS process for $π^+$ and $π^-$ channels. We use a recently proposed light-front quark-diquark model for proton with the light-front wave functions predicted in soft-wall AdS/QCD. The model predictions are compared with the HERMES and COMPASS data.
Understanding the role of Cahn and Sivers effects in Deep Inelastic Scattering
内禀$k_\perp$在半包容深非弹性散射（SIDIS）过程中的作用在QCD部分子模型中，在首阶下研究了（$l p \to l h X$）的精确运动学;非极化截面对轻子和强子产生面之间方位角的依赖性（Cahn效应）与实验数据进行了比较，并用于估算夸克分布函数和碎裂函数中的$k_\perp$平均值。由此产生的图片适用于描述的加权单自旋不对称性$A_{UT}^{\sin(ϕ_π- ϕ_S)}$最近测量的HERMES合作在DESY，这使得提取参数的夸克Sivers功能。提取的Sivers功能给出的COMPASS测量的$A_{UT}^{\sin(ϕ_π- ϕ_S)}$与最近的数据一致的预测，而他们的贡献HERMES $A_{UL}^{\sinϕ_π}$计算和发现是小的。对HERMES产生K介子的$A_{UT}^{\sin(ϕ_K - ϕ_S)}$也作了预测。
In this paper we study the single spin asymmetry $A_{UT}^{\sin(ϕ_h-ϕ_S)}$ of a single hadron production in semi-inclusive deep inelastic scattering (SIDIS) within the framework of transverse momentum dependent (TMD) factorization up to next-to-leading logarithmic (NLL) order of QCD. The asymmetry is contributed by the convolution of the Sivers function and the unpolarized fragmentation function. Specifically, the Sivers function in the coordinate space and perturbative region can be represented as the convolution of the $C$-coefficients and the corresponding collinear correlation functions, am…
A major part of the future COMPASS program is dedicated to the investigation of the nucleon structure through Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Production (DVMP). COMPASS will measure DVCS and DVMP reactions with a high intensity muon beam of 160 GeV and a 2.5 m-long liquid hydrogen target surrounded by a new TOF system. The availability of muon beams with high energy and opposite charge and polarization will allow to access the Compton form factor related to the dominant GPD $H$ and to study the $x_{B}$-dependence of the $t$-slope of the pure DVCS cross section…
The COMPASS experiment at CERN is one of the leading experiments studying the nucleon spin structure. Until 2012 the Parton Distribution Functions and the Transverse Momentum Dependent Parton Distribution Functions (TMDs) were extensively studied at COMPASS using Semi-Inclusive Deep Inelastic Scattering measurements. In 2015, the Drell-Yan measurements with a negative pion beam interacting with a transversely polarized ammonia target have started and will be continued through 2018. The goal is to access the TMDs of both pions and protons without any prior knowledge about fragmentation function…
One of the important objectives of the COMPASS experiment (CERN, SPS north area) is the exploration of transverse spin structure of nucleon via study of spin (in)dependent azimuthal asymmetries with semi-inclusive deep inelastic scattering (SIDIS) processes and recently also with Drell-Yan (DY) reactions. In the past twelve years series of measurements were made in COMPASS, using 160 GeV/c longitudinally polarized muon beam and polarized $^6LiD$ and $NH_3$ targets. Drell-Yan measurements with high energy (190 GeV/c) pion beam and transversely polarized $NH_3$ target started in 2014 with a pilo…
