The past seventeen years have witnessed tremendous progress on the experimental and
theoretical explorations of the multiquark states. The hidden-charm and hidden-bottom …

In the past two decades, a plethora of hadronic states beyond the conventional quark model
of qq ̄ mesons and qqq baryons have been observed experimentally, which motivated …

Multiquark resonances are undoubtedly experimentally observed. The number of states and
the amount of details on their properties have been growing over the years. It is very recent …

This review presents an overview of the remarkable progress in the field of heavy-quark
exotic hadrons over the past 15 years. It seeks to be pedagogical rather than exhaustive …

In the past decade many charmonium-like states were observed experimentally. Especially
those charged charmonium-like Z c states and bottomonium-like Z b states cannot be …

The existence and properties of the sigma meson have been controversial for almost six
decades, despite playing a central role in the spontaneous chiral symmetry of QCD or in the …

The last decade has seen a marked shift in how the internal structure of hadrons is
understood. Modern experimental facilities, new theoretical techniques for the continuum …

A golden age for heavy-quarkonium physics dawned a decade ago, initiated by the
confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of …

For many decades after the invention of the quark model in 1964 there was no evidence that
hadrons are formed from anything other than the simplest pairings of quarks and antiquarks …

This biennial Review summarizes much of particle physics. Using data from previous
editions, plus 2158 new measurements from 551 papers, we list, evaluate, and average …