Transverse single spin asymmetry ine+p↑→e+J/ψ+Xand

Rohini M. Godbole

¹

,

Abhiram Kaushik²,

Anuradha Misra³

et al.

Abstract

We present estimates of Single Spin Asymmetry (SSA) in the electroproduction of J/ψ taking into account the transverse momentum dependent (TMD) evolution of the gluon Sivers function. We estimate SSA for JLab, HERMES, COMPASS and eRHIC energies using color evaporation model of J/ψ. We have calculated the asymmetry using recent parameters extracted by Echevarria et al. using the CSS approach to TMD evolution. These recent TMD evolution fits are based on the evolution kernel in which the perturbative part is resummed up to next-to-leading logarithms (NLL) accuracy. We have also estimated the asymmetry by using parameters which had been obtained by a fit by Anselmino et al., using both an exact numerical and an approximate analytical solution of the TMD evolution equations. We find that the variation among the different estimates obtained using TMD evolution is much smaller than between these on one hand and the estimates obtained using DGLAP evolution on the other. Even though the use of TMD evolution causes an overall reduction in asymmetries compared to the ones obtained without it, they remain sizable. Overall, upon use of TMD evolution, predictions for asymmetries stabilize.

$$J/\psi $$ J / ψ production in polarized and unpolarized ep collision and Sivers and $$\cos 2\phi $$ cos 2 ϕ asymmetries

“…We follow the generalized factorization theorem where the intrinsic partonic transverse momentum is taken into account, unlike the collinear factorization. The kinematics considered below is different from [39][40][41]. We consider the frame as shown in Fig.…”

“…In Refs. [39][40][41], SSA in J/ψ production in ep ↑ collision using a low virtuality electroproduction approximation (photoproduction) is studied in a color evaporation model (CEM) and sizable asymmetries are reported. In this work the Sivers asymmetry in the semi-inclusive process e + p ↑ → e + J/ψ + X and the cos 2φ azimuthal asymmetry in the unpolarized process e + p → e + J/ψ + X using a non-relativistic Quantum Chromo Dynamics (NRQCD)-based color octet model (COM) [47] are investigated.…”

“…Moreover, one of the gluon Sivers functions (d-type) is not constrained by Burkardt's sum rule. Apart from the SIDIS and the DY [36][37][38], the Sivers effect has been studied theoretically in several ep ↑ collision processes; among them photoproduction of J/ψ [39][40][41], heavy quark pair and dijet production in ep ↑ scattering [42]. In the SSA in proton-proton collision the process-dependent initial and final state interactions play a major role and usually need to be carefully taken into account [43].…”

Towards a first estimate of the gluon Sivers function from A N data in pp collisions at RHIC

“…the polarized proton) [66]; back-to-back azimuthal correlations in two-jet production [67]; SSAs in inclusive D meson production at RHIC [68]; SSAs in J/ψ electroproduction with transversely polarized electron and proton beams [69]. A detailed and updated discussion on the gluon Sivers function and additional references can be found in ref.…”

Transverse single-spin asymmetry in the low-virtuality leptoproduction of open charm as a probe of the gluon Sivers function

“…The low-virtuality leptoproduction of J=ψ has also been suggested as a probe of the GSF [13][14][15]. However, leptoproduction of open-charm may have some more advantages over the above mentioned processes.…”