Search for exotic charmonium states

TL;DR

This paper reviews and compares experimental results from BABAR and Belle on charmonium-like states, discussing their potential exotic nature and the challenges they pose to existing theoretical models in hadron spectroscopy.

Contribution

It synthesizes experimental findings from BABAR and Belle on specific invariant mass systems to evaluate the evidence for exotic charmonium states and discusses their implications for theory.

Findings

Evidence suggests possible exotic or hybrid states in the analyzed mass distributions.

Standard potential models struggle to explain the observed enhancements.

Comparative analysis highlights the need for new theoretical approaches.

Abstract

One of the most intriguing puzzles in hadron spectroscopy are the numerous charmonium-like states observed in the last decade, including charged states that are manifestly exotic. The $BABAR$ and Belle experiments have extensively studied those in B meson decays, initial state radiation processes and two photon reactions. We can question what we have understood after 11 year search in this field, and try to combine results to conclude on what these new unpredicted resonant states are, and how they can be accommodated in the theory. Big effort has been made from theoretical and experimental point of view, as the potential models unlikely explain the presence of so many enhancements, for mass values above the $D \bar D$ threshold. In this report the $BABAR$ and Belle results of the two invariant mass systems of $J/\psi \phi$ and $J/\psi \omega$ are put in comparison in a search for non-conventional charmonium states. This involves the study of the systems of $J/\psi K^+ K^-$ and $J/\psi \pi^+ \pi^- \pi^0$, respectively. There are strong theoretical arguments in favor of the presence of hybrids or exotic states, in those invariant mass distributions. Remarks on these data analyses are given, based on the $BABAR$ and Belle experimental results.