A large number of experimental discoveries especially in the heavy quarkonium sector that
did not meet the expectations of the until then very successful quark model led to a …

In this review, we present the current state of the art of our understanding of the spectrum of
excited strongly interacting particles and discuss methods that allow for a systematic and …

Chiral perturbation theory and its unitarized versions have played an important role in our
understanding of the low-energy strong interaction. Yet, so far, such studies typically deal …

In the past two decades, one of the most puzzling phenomena discovered in hadron physics
is that a nominal hadronic state can actually correspond to two poles on the complex energy …

The description of strong interaction physics of low-lying resonances is out of the valid range
of perturbative QCD. Chiral effective field theories (EFTs) have been developed to tackle the …

During its long-lasting history, the Λ (1405) has become a benchmark for our understanding
of the SU (3) hadron dynamics. Starting with its theoretical prediction and later experimental …

The strange quark plays a unique role in QCD, reflecting its intermediate mass between the
light and heavy quarks. In recent years, remarkable progress has been made in the …

The two-pole structure refers to the fact that particular single states in the spectrum as listed
in the PDG tables are often two states. The story began with the Λ (1405), when in 2001 …

Two-particle momentum correlation functions as measured in heavy ion collisions or in high-
energetic proton–proton collisions are studied. Special emphasis is put on systems like ΛΛ …

Kaonic atoms are an extremely efficient tool to investigate the strong interaction at the low
energy Frontier, since they provide direct access to the K− N interaction at threshold …