5 pages, 6 figures, To appear in the proceedings of the 12th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon (MENU 2010), May 31- June 4, 2010, Williamsburg VA, USA
The non-vanishing of naive T-odd parton distributions function can be explained by the existence of the gauge link which emerges from the factorized description of the deep inelastic scattering cross section into perturbatively calculable and non-perturbative factors. This path ordered exponential describes initial / final-state interactions of the active parton due to soft gluon exchanges with the target remnants. Although these interactions are non-perturbative, studies of final state interactions have been approximated by perturbative one-gluon exchange in Abelian models. We include higher-order gluonic contributions from the gauge link by applying non-perturbative eikonal methods, incorporating color degrees of freedom in a calculation of the Sivers function. In this context we study the effects of color by considering the FSIs with Abelian and non-Abelian gluon interactions. We confirm the large $N_c$ QCD scaling behavior of Sivers functions and further uncover the deviations for finite $N_c$. Within this framework of FSIs we perform a quantitative check of approximate relations between T-odd TMDs and GPD which goes beyond the discussion of overall signs.
The Gluon Sivers Distribution in D production at RHIC
RHIC D介子产生中的单横自旋不对称性可以提供胶子Sivers分布函数的一个干净的度量。在中等快度下,D的产生主要由基本的gg -> c c-bar通道控制,在那里不可能有任何横向自旋转移。因此,在极化质子-质子相互作用中所观察到的D's的任何横向单自旋不对称性只能源于胶子分布函数中的Sivers效应。由PHENIX或STAR实验测量的相当大的横向单自旋不对称性将给出关于胶子西弗斯分布函数大小的直接信息。
We calculate the Sivers function of $\bar{u}$ and $\bar{d}$ quarks using the overlap representation within the light-cone formalism. The light-cone wave functions of the proton is obtained in terms of the $|\bar{q} q B\rangle$ Fock states motivated by the meson-baryon fluctuation model. We consider the final-state interaction at the level of one gluon exchange. In a simplified scenario, the Sivers function of $\bar{u}$ and $\bar{d}$ can be expressed as the convolution of the Sivers function of the pion inside the proton and the unpolarized distribution of $\bar{q}$ inside the pion. The model p…
We investigate the single transverse-spin asymmetry with a $\sin (ϕ_h-ϕ_S)$ modulation in the charged Kaon produced and in $Λ$ hyperon produced SIDIS process within the theoretical framework of transverse momentum dependent (TMD) factorization at the next-to-leading-logarithmic order. The asymmetry is contributed by the convolution of Sivers function and the unpolarized fragmentation function $D_1$ for the produced hadron. The parametrization for the proton Qiu-Sterman function, which is closely related to the Sivers function, is adopted to numerically estimate the Sivers asymmetry at the kine…
We present estimates of transverse single-spin asymmetry in prompt photon production in the scattering of low virtuality photons off a polarized proton target and discuss the possibility of using this as a probe to get information about the gluon Sivers function (GSF). Using a generalized parton model (GPM) framework, we estimate the asymmetries at electron-ion collider energy ($\sqrt{s}$ =140 GeV) taking into account both direct and resolved photon processes and find that the dominant contribution, up to $10\%$, comes from quark Sivers function (QSF) while the contribution from GSF is found t…
We study the Sivers azimuthal asymmetry for $J/ψ$ production in semi-inclusive deep inelastic scattering, and the still poorly known gluon Sivers function. We concentrate on the $J/ψ$ low transverse momentum region, employing the transverse-momentum dependent generalised parton model (GPM), and its colour gauge invariant extension (CGI-GPM), which includes final-state interactions at leading order. We adopt the nonrelativistic QCD (NRQCD) framework for the quarkonium formation mechanism, and compare our results for the unpolarised cross section and the Sivers asymmetry with available data, res…
We consider the transverse single-spin asymmetry (SSA) for $J/ψ$ production in $p^\uparrow p \to J/ψ+ X$ within a TMD approach in non-relativistic QCD. Extending a previous study [1], we employ here the color-gauge invariant generalized parton model (CGI-GPM), in which spin and intrinsic transverse momentum effects are taken into account, together with leading-order initial- and final-state interactions (ISIs and FSIs). We find that, even when the heavy-quark pair is produced in a color-octet state, ISIs and FSIs lead to a nonvanishing SSA, allowing, in principle, to test the process dependenc…
In this contribution, we will present a short overview of the transverse momentum dependent (TMD) approach as a tool for studying the 3-dimensional structure of hadrons in high-energy (un)polarized hadron collisions. We will then summarize the present status of a running research programme that aims at constraining the poorly known transverse momentum dependent gluon Sivers function, through the study of single spin asymmetries in quarkonium (mainly $J/ψ$), pion, and $D$-meson production in polarized proton-proton collisions at RHIC. Finally, we will shortly discuss perspectives for this field…
Northwestern University(西北大学);Stony Brook University(纽约州立大学石溪分校);Beijing Normal University(北京师范大学);Institute of Modern Physics, Chinese Academy of Science(中国科学院近代物理研究所)
Extension of the non-pole technique to the twist-3 gluon distribution contribution in $pp$ collisions
Institute of Nuclear Physics Polish Academy of Sciences(波兰科学院核物理研究所);State Key Laboratory of Nuclear Physics and Technology, Institute of Quantum Matter, South China Normal University(华南大学量子物质研究所核物理与技术国家重点实验室);Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, Guangdong Provincial Key Laboratory of Nuclear Science(广东省基础研究中心物质结构与基本相互作用卓越中心广东省核科学重点实验室)