Probing the gluon Sivers function in p↑p→J/ψ X and

Abstract

We present a study of transverse single-spin asymmetries (SSAs) in p ↑ p → J/ψ X and p ↑ p → DX within the framework of the generalized parton model (GPM), which includes both spin and transverse momentum effects, and show how they can provide useful information on the still almost unknown gluon Sivers function. Moreover, by adopting a modified version of this model, named color gauge invariant (CGI) GPM, we analyze the impact of the initial-and final-state interactions on our predictions. As a consequence, we find that these two processes are sensitive to different gluon Sivers functions, which can be expressed as linear combinations of two distinct, universal gluon distributions. We therefore define proper observables which could allow for a separate extraction of these two independent Sivers functions. At the same time, we show how it would be possible to discriminate between the GPM and the CGI-GPM approaches by comparing the corresponding estimates of SSAs with present and future experimental results at RHIC.

Transverse single spin asymmetry in p+p↑→J/ψ+X

“…A similar comparison with PHENIX results has been performed recently in Ref. [32] using colour singlet model (CSM) and a maximized GSF, whereas in our work we use CEM and compare various parameterizations of GSF available. We also present estimates of asymmetry for future proposed experiments at AFTER@LHC which is a fixed target experiment with √ s = 115 GeV and for √ s = 500 GeV which will be explored at RHIC.…”

“…Here, we use a phenomenological approach referred to in literature as the Generalized Parton Model (GPM), which has been used to estimate SSAs in several processes like 24,32,35], pp ↑ → γ + jet + X [23,26] and pp ↑ → π + X [9] for which TMD factorization has not yet been established. A rigorous treatment will require inclusion of intrinsic transverse momentum effects through a consideration of higher twist effects.…”

“…Heavy flavour production-both open and closed-are considered to be clean probes of the GSF since heavy quarks are predominantly produced via gluon-gluon fusion and thus can be used to isolate gluon dynamics within hadrons [24,[28][29][30][31][32]. The possibility of getting information on the GSF by looking at D-meson production in polarized proton-proton scattering at RHIC has been discussed by Anselmino et al [24] using a saturated GSF.…”

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

“…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].…”

Sivers effect in inelastic J/ψ photoproduction in ep↑ collision in color octet model

“…Heavy quarkonium production in ep [19][20][21][22][23] and pp [24,25] collision has been studied theoretically quite extensively for probing the gluon TMDs, in particular the GSF and linearly polarized gluon distribution [26,27]. This is because the heavy quarkonium is produced at leading order (LO) through photon-gluon fusion (ep) or two gluon fusion (pp) channel.…”