Abstract
The prediction of single-spin asymmetry in inelastic photoproduction of $J/\psi$ in $ep^\uparrow$ collision is presented. At next-to-leading order, the dominating process is photon-gluon fusion, $\gamma+g\rightarrow J/\psi+g$ for the production of $J/\psi$ in $e+p^\uparrow\rightarrow J/\psi+X$, which directly probes the gluon Sivers function. Using the non-relativistic QCD based color octet model, the color octet states $\leftidx{^{3}}{S}{_1}^{(8)}$, $\leftidx{^{1}}{S}{_0}^{(8)}$ and $\leftidx{^{3}}{P}{_{J(0,1,2)}}^{(8)}$ contribution to $J/\psi$ production is calculated. Sizable asymmetry is estimated as a function of transverse momentum $P_T$ and energy fraction $z$ of $J/\psi$ in the range $0<P_T\leq 1$ GeV and $0.3<z\leq 0.9$. The unpolarized differential cross section of inelastic $J/\psi$ photoproduction is found to be in good agreement with H1 and ZEUS data.
Highlights
Among the transverse momentum dependent pdfs (TMDs), Sivers function has attracted considerable interest in the scientific community in recent days, largely because of a large amount of experimental results coming in
The nonzero Sivers function gives a coupling between the intrinsic transverse momentum of the parton and the transverse spin of the nucleon [1,2], this gives an azimuthal asymmetry in the distribution of the final state particle in ep↑ and pp↑ collision that has been measured at HERMES [3,4,5], COMPASS [6,7,8,9], JLAB [10,11] and RHIC [12,13] respectively
The next-to-leading order (NLO) subprocess γ þ g → J=ψ þ g is considered for J=ψ production in ep↑ → J=ψ þ X
Summary
Among the transverse momentum dependent pdfs (TMDs), Sivers function has attracted considerable interest in the scientific community in recent days, largely because of a large amount of experimental results coming in. The initial and final state interactions (gauge links) play an important role in the Sivers asymmetry This gives a dependence on the specific process in which the Sivers function is studied. This gives systematic way to separate the high energy and low energy effects of the production mechanism In this approach, the heavy quark pair is produced at a short distance in color singlet (CS) [29,30,31,32] or in color octet (CO) [33,34,35] configuration and they hadronize to form a quarkonium state of given quantum numbers through a soft process. The final state interactions are more involved for pp collision processes, and there, nonzero SSA is expected when the heavy quark pair is produced in a CS state. A few details of calculation are given in the Appendices
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
