Impact of $\eta_c$ hadroproduction data on charmonium production and polarization within NRQCD framework

Understand

With the recent LHCb data on $\eta_c$ production and based on heavy quark spin symmetry, we obtain the long-distance matrix elements for both $\eta_c$ and $J/\psi$ productions, among which, the color-singlet one for $\eta_c$ is obtained directly by the fit of experiment for the first time.

• Using our long-distance matrix elements, we can provide good description of the $\eta_c$ and $J/\psi$ hadroproduction measurements.
• Our predictions on $J/\psi$ polarization are in good agreement with the LHCb data and pass through the two sets of CDF measurements in medium $p_t$ region.
• Considering all the possible uncertainties carefully, we obtained quite narrow bands of the $J/\psi$ polarization curves.