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

TL;DR

This paper uses recent LHCb data and heavy quark spin symmetry within the NRQCD framework to determine long-distance matrix elements, successfully describing $ ext{eta}_c$ and $J/ ext{psi}$ production and polarization.

Contribution

It provides the first direct fit of the color-singlet long-distance matrix element for $ ext{eta}_c$ production using experimental data within NRQCD.

Findings

Good agreement with $ ext{eta}_c$ and $J/ ext{psi}$ production data

Predictions match $J/ ext{psi}$ polarization measurements

Narrow uncertainty bands for polarization curves

Abstract

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.