Are the $Y$ states around 4.6 GeV from $e^+e^-$ annihilation higher charmonia?

TL;DR

This paper investigates the nature of Y states around 4.6 GeV, proposing they are higher charmonia states, supported by combined experimental data analysis and theoretical modeling, predicting their properties and decay behaviors.

Contribution

The study introduces a combined fit to experimental data revealing two resonances and suggests these Y states are mixtures of higher charmonium states, providing new insights into their structure.

Findings

Identified two resonances at 4585 MeV and 4676 MeV with specific widths.

Supported the interpretation of Y states as higher charmonia with mixed S-D wave components.

Predicted masses and decay modes for six higher charmonia states above 4.6 GeV.

Abstract

In this work, we present the mass spectrum of higher charomona around and above 4.6 GeV by adopting the unquenched potential model. We perform a combined fit to the updated experimental data of $e^+e^- \to \psi(2S)\pi^+\pi^-$ and $e^+e^-\to \Lambda_c\bar{\Lambda}_c$. To understand the "platform" structure observed in the range of $4.57 \sim 4.60$ GeV existing in the $\Lambda_c\bar{\Lambda}_c$ invariant mass spectrum of $e^+e^-\to \Lambda_c\bar{\Lambda}_c$ of BESIII, we introduce two resonances in this combined fit to the $e^+e^- \to \psi(2S)\pi^+\pi^-$ and $e^+e^-\to \Lambda_c\bar{\Lambda}_c$, which have resonance parameters, $m_{Y_1}=4585\pm2$ MeV, $\Gamma_{Y_1}=29.8\pm8.0$ MeV, $m_{Y_2}=4676\pm7$ MeV, and $\Gamma_{Y_2}=85.7\pm15.0$ MeV. Furthermore, combining with our theoretical results, we indicate that the two charmonium-like $Y$ states can be due to two higher charmonia, which are mixtures of $6S$ and $5D$ $c\bar{c}$ states. Their two-body open-charm decay behaviors are given. Under the same framework, our analysis of the data of $e^+e^-\to D_{s}^+D_{s1}(2536)^-$ recently released by Belle supports to introduce these two higher charmonia around 4.6 GeV. Additionally, we predict the masses and two-body open-charm decays of six higher charmonia $\psi(nS)$ and $\psi(mD)$ with $n=7,8,9$ and $m=6,7,8$ above 4.6 GeV. Search for these higher charmonia will be an interesting issue for the running BESIII and BelleII, and even the possible Super Tau-Charm Factory discussed in China.