Speaker
Description
We present an estimate of azimuthal asymmetry ($cos~2\phi$) in $J/\psi$ production in electron-proton collision within the kinematics of the planned electron-ion collider (EIC). We find a small but a sizable asymmetry in the small $x$ region which can be observed at the EIC. This sizable asymmetry directly probes the Weisz\"{a}ker-Williams (WW) type linearly polarized gluon distribution in unpolarized proton. We assume generalized factorization and calculate the asymmetry at next-to-leading order in the kinematical region which satisfies, energy fraction of $J/\psi$, $z<1$ and the subprocess $\gamma^* +g \rightarrow c + {\bar c}+g$ gives the leading contribution. We use color-singlet model, based on non-relativistic QCD (NRQCD), for $J/\psi$ production. We estimate the asymmetry in two models: (i) Gaussian type parameterization of the TMDs and (ii) McLerran-Venugopalan (MV) model at small $x$ and also we present the upper bound of the asymmetry. All three cases estimate a small but sizable asymmetry in the considered kinematical region. So, observing a $cos~2\phi$ asymmetry in $J/\psi $ production at EIC will give information on linearly polarized gluon distribution.
