Accessing Linearly Polarized Gluon Distribution in $J/\psi$ Production at the Electron-Ion Collider

Abstract

We calculate the $cos2\varphi$ asymmetry in $J/\psi$ production in electron-proton collision for the kinematics of the planned electron-ion collider (EIC). This directly probes the Weiszäcker-Williams (WW) type linearly polarized gluon distribution. Assuming generalized factorization, we calculate the asymmetry at next-to-leading-order (NLO) when the energy fraction of the $J/\psi$ satisfies $z<1$ and the dominating subprocess is ${\gamma }^{\ast }+g\to c+\bar{c}+g$. We use non-relativistic QCD based color singlet model for $J/\psi$ production. We investigate the small $x$ region which will be accessible at the EIC. We present the upper bound of the asymmetry, as well as estimate it using a (i) Gaussian type parametrization for the TMDs and (ii) McLerran-Venugopalan model at small $x$. We find small but sizable asymmetry in all the three cases.

Version to appear in Phys. Rev. D

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• The $\cos 2\varphi$ azimuthal asymmetry in ${\rho }^0$ meson production in ultraperipheral heavy ion collisions
• Sivers Asymmetry in Photoproduction of $J/\psi$ and Jet at the EIC
• Sub-femtometer scale color charge correlations in the proton
• Prospects for quarkonium studies at the high-luminosity LHC
• $\cos 2{\varphi }_t$ azimuthal asymmetry in back-to-back $J/\psi$-jet production in $ep\to eJ/\psi JetX$ at the EIC
• Gluon Polarimetry with Energy-Energy Correlators
• Azimuthal asymmetries in $D$-meson and jet production at the EIC