The prompt $J/\psi$ production in Association with a $c\bar{c}$ Pair within the Framework of Non-relativistic QCD via photon-photon collision at the International Linear Collider

TL;DR

This paper studies prompt $J/$ production with a $c\bar{c}$ pair via photon-photon collisions at the ILC, highlighting the dominance of color-octet channels and their impact on polarization and cross-sections.

Contribution

It provides a systematic analysis of $J/\psi$ production including both direct and feed-down contributions within NRQCD at the ILC, emphasizing the role of color-octet states.

Findings

Color-octet channels dominate the production cross-section.

Feed-down from $'$ and $_{J}$ contributes about 20%.

Polarization varies from longitudinal at low $p_t$ to transverse at high $p_t$.

Abstract

We present a systematical study on the prompt $J/\psi$ production in association with a $c\bar{c}$ pair via the process, $\gamma\gamma \to H(c\bar{c}) +c+\bar{c}$, within the framework of non-relativistic QCD at the future high-energy $e^{+}e^{-}$ collider - International Linear Collider (ILC), including both direct and feed-down contributions. For direct $J/\psi$ production, the states with color-octet channels, especially the $^3P_J^{[8]}$ and $^1S_0^{[8]}$ ones, provide dominant contribution to the production cross-section, which are about fifty-two times over that of the color-singlet one. This is clearly shown by the transverse momentum ($p_t$) and rapidity distributions. The feed-down contribution from $\psi'$ and $\chi_{cJ}$ ($J=0,1,2$) is sizable, which is about $20\%$ to the total prompt cross-section. Besides the yields, we also calculate the $J/\psi$ polarization parameter $\lambda$. In small $p_t$ region, the polarization of the prompt $J/\psi$ is longitudinal due to large contributions through the $^3P_J^{[8]}$ channel, and becomes transverse in high $p_t$ region due to $^3S_1^{[8]}$ channel. Thus the $J/\psi$ production via photon-photon collisions at the ILC shall provide a useful platform for testing the color-octet mechanism.