Extraction of the Sivers function from SIDIS, Drell-Yan, and $W^\pm/Z$ boson production data with TMD evolution

Abstract

We perform a global fit of the available polarized Semi-Inclusive Deep Inelastic Scattering (SIDIS), polarized pion-induced Drell-Yan (DY) and W ± /Z boson production data at N 3 LO and NNLO accuracy of the Transverse Momentum Dependent (TMD) evolution, and extract the Sivers function for u, d, s and for sea quarks. The Qiu-Sterman function is determined in a model independent way via the operator product expansion from the extracted Sivers function. The analysis is supplemented by additional studies, such as the estimation of applicability region, the impact of the unpolarized distributions' uncertainties, the universality of the Sivers functions, positivity constraints, the significance of the sign-change relation, and the comparison with the existing extractions.

Nucleon transverse quark spin densities

“…4, is rapidly decreasing resulting in a large distortion. The origin of this behavior is related to the Sivers effect [16], a connection that was made in Ref. [15]; iii) Transversely polarized quarks in a transversely polarized nucleon, where all the terms in Eq.…”

Nucleon transverse quark spin densities

“…𝑢-𝑑 𝑢 𝑑 𝑠 𝑐 𝑔 𝑇 0.936(25) 0.729(22) -0.207(75) -0.00268(58) -0.00024 (16) Table 3: We give our values for 𝑔 𝑇 extracted using the cB211.072.64 ensemble: first column for 𝑔 𝑢−𝑑 𝑇 and the 2 nd to 5 th for 𝑔 𝑢 𝑇 , 𝑔 𝑑 𝑇 , 𝑔 𝑠 𝑇 , 𝑔 𝑐 𝑇 , respectively [6]. The values are given in the MS scheme at 2 GeV.…”