Exotics at Belle and perspectives at Belle II

TL;DR

This paper reviews recent discoveries of exotic multi-quark states at Belle and discusses future prospects at Belle II, highlighting the need to go beyond the traditional quark model in understanding hadron spectroscopy.

Contribution

It summarizes recent experimental results on exotic states and outlines the future research directions at Belle II to explore beyond the constituent quark model.

Findings

Discovery of the X(3872) in 2003 at Belle

Evidence of states not explained by the traditional quark model

Future prospects for exotic hadron searches at Belle II

Abstract

The search for multi-quark states beyond the constituent quark model (CQM) has resulted in the discovery of many new exotic states, starting with the observation of the X(3872), discovered by Belle in 2003. Also in the sector of charm-strange physics the CQM does not seem to describe properly all spectrum, despite of theoretical expectations. These new forms of quark bounds clearly show that mesons and baryons are not the only possibilities to be considered. We shortly report in this paper selected recent results on searching for such states at Belle, with the perspectives in the hadron physics program at the Belle II experiment.