Global analysis of the Sivers functions at NLO+NNLL in QCD
A bstract We perform global fit to the quark Sivers function within the transverse momentum dependent (TMD) factorization formalism in QCD. We simultaneously fit Sivers asymmetry data from Semi-Inclusive Deep Inelastic Scattering (SIDIS) at COMPASS, HERMES, and JLab, from Drell-Yan lepton pair production at COMPASS, and from W/Z boson at RHIC. This extraction is performed at next-to-leading order (NLO) and next-to-next-to leading logarithmic (NNLL) accuracy. We find excellent agreement between our extracted asymmetry and the experimental data for SIDIS and Drell-Yan lepton pair production, while tension arises when trying to describe the spin asymmetries of W/Z bosons at RHIC. We carefully assess the situation, and we study in details the impact of the RHIC data and their implications through different ways of performing the fit. In addition, we find that the quality of the description of W/Z vector boson asymmetry data could be strongly sensitive to the DGLAP evolution of Qiu-Sterman function, besides the usual TMD evolution. We present discussion on this and the implications for measurements of the transverse-spin asymmetries at the future Electron Ion Collider.
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Publication Date:
NSF-PAR ID:
10281180
Journal Name:
Journal of High Energy Physics
Volume:
2021
Issue:
1
ISSN:
1029-8479
4. Abstract We propose a new observable for the measurement of the forward–backward asymmetry $$(A_{FB})$$ ( A FB ) in Drell–Yan lepton production. At hadron colliders, the $$A_{FB}$$ A FB distribution is sensitive to both the electroweak (EW) fundamental parameter $$\sin ^{2} \theta _{W}$$ sin 2 θ W , the weak mixing angle, and the parton distribution functions (PDFs). Hence, the determination of $$\sin ^{2} \theta _{W}$$ sin 2 θ W and the updating of PDFs by directly using the same $$A_{FB}$$ A FB spectrum are strongly correlated. This correlation would introduce large bias or uncertainty into both precise measurements ofmore »