Studies of quarkonium at Belle and Belle II

TL;DR

This paper reviews recent findings on quarkonium from Belle and Belle II experiments, highlighting discoveries of conventional and exotic states, and discusses the enhanced capabilities of Belle II for future research in this field.

Contribution

It presents new results from Belle on bottomonium decays and discusses how Belle II's upgraded detector will advance quarkonium studies with larger data sets.

Findings

Discovery of new bottomonium decay modes

Observation of unconventional quarkonium-like states

Enhanced potential for quarkonium research with Belle II

Abstract

Quarkonium is the bound state of a heavy quark and its anti-quark counterpart. The study of this system has experienced a renaissance thanks to results from e+e- collider experiments, including discoveries of long-predicted conventional quarkonia, and unusual states consisting of four quarks. The Belle Experiment operated at KEK in Japan from 1999-2010. Analysis of the collected data continues to produce new findings. The Belle II experiment is a substantial upgrade of both the Belle detector and the KEKB accelerator, aiming to collect 50 times more data beginning in 2018. This talk presented recent Belle results related to hadronic and radiative decays in the bottomonium system. It described the capabilities of Belle II to explore these topics, with a particular focus on the physics reach of the first data, where unique opportunities exist to make an immediate impact in this area.