Charmonia and exotics from BESIII

TL;DR

This paper reviews recent BESIII findings of new charmonium-like states, including the $Z_c(3900)$ and $Z_c(4020)$, which suggest the existence of exotic four-quark matter beyond traditional meson models.

Contribution

It provides a comprehensive overview of recent experimental discoveries of exotic states that challenge conventional quark-model classifications.

Findings

Identification of $Z_c(3900)$ and $Z_c(4020)$ states

Evidence for states coupling to light mesons and heavy charmonium

Implication of four-quark matter existence

Abstract

Several states that couple to one light-meson and a heavy-charmonium are recently reported, including the $Z_c(3900)$ and $Z_c(4020)$. These states cannot be interpreted within the constituent quark-model of mesons, and are good candidates for a new form of quark matter, four-quark matter. A review of recent results on new charmonium-like states studied at BESIII is presented.