Some recent progress in understanding exclusive double charmonium production at $B$ factories

TL;DR

This paper reviews recent theoretical progress in understanding exclusive double charmonium production at B factories, focusing on perturbative, relativistic, and helicity suppression effects within the NRQCD framework.

Contribution

It discusses the impact of combined perturbative and relativistic corrections on key processes and highlights new theoretical challenges in applying NRQCD to helicity-suppressed reactions.

Findings

Relativistic corrections significantly affect $e^+e^-\to J/\psi+\eta_c$ predictions.

Next-to-leading order perturbative corrections influence $e^+e^-\to J/\psi+\chi_{cJ}$ processes.

Helicity suppression presents a new challenge for NRQCD in heavy quarkonium production.

Abstract

We review some recent progress in understanding various exclusive double charmonium production processes at $B$ factories, within the nonrelativistic QCD factorization framework. First we investigate the impact of the joint perturbative and relativistic correction on the process that has attracted a great amount of attention in the past decade, $e^+e^-\to J/\psi+\eta_c$. We then briefly discuss the phenomenological implication of the next-to-leading order perturbative correction to the processes $e^+e^-\to J/\psi+\chi_{c0,1,2} (\eta_{c2})$. We further emphasize a novel theoretical challenge, which is recently discovered by applying the NRQCD factorization approach to the helicity-suppressed hard exclusive reactions involving heavy quarkonium.