Four sorts of meson

An extensive spectrum of light non-strange qq-macron states up to a mass of 2400 MeV has emerged from Crystal Barrel and PS172 data on p-macron p→Resonance→A+B in 17 final states. These data are reviewed with detailed comments on the status of each resonance. For I=0, C=+1, the spectrum is complete and very secure. Six 'extra' states are identified. Four of them have I=0, C=+1 and spin-parities predicted for glueballs. Their mass ratios agree closely with predictions from lattice QCD calculations. However, branching ratios for decays are not flavour blind and require mixing with neighbouring qq-bar states. This mixing remains controversial. Two further states, η2(1870) and π2(1880), are candidates for a pair of hybrids. Their decay branching ratios BR[η2(1870)→f2(1270)η]/BR[η2(1870)→a2(1320)π] and BR[π2(1880)→a2(1320)η]/BR[π2(1880)→f2(1270)π] are much larger than predicted by SU(3) for qq-bar states. A fourth category of anomalously light 0+ mesons is made of σ(540), κ(750), a0(980) and f0(980), forming a non-qq-macron nonet. Their properties are reviewed using data from both Crystal Barrel and elsewhere