[en] Evidence for the σ pole has been reported in production processes such as D⁺→π⁺π^-π⁺; likewise evidence for the κ pole appears in D⁺→K^-π⁺π⁺. Their effects in ππ and Kπ elastic scattering are much less conspicuous. However, consistent fits to both production data and elastic scattering may be obtained by including the Adler zero into an s-dependent width for each resonance. These zeros suppress strongly the effects of the σ and κ poles in elastic scattering; the zeros are absent from amplitudes for production data. With this prescription, data from ππ→ππ, K_e4 decays and CP violation in K⁰ decays give a σ pole position of (525±40)-i(247±25) MeV. A combined analysis with production data gives a better determination of (533±25)-i(249±25) MeV. The analysis of LASS data for Kπ elastic scattering, including the Adler zero, determines a κ pole at (722±60)-i(386±50) MeV. The Fourier transform of the matrix element for σ→ππ reveals a compact interaction region with RMS radius ∼0.4 fm

[en] Crystal Barrel data reveal systematics of qqbar resonances up to 2410 MeV. In particular, all expected J^PC = 2⁺⁺ I = 0 qqbar states may be identified in this range of masses M. For most J^PC, observed resonances lie close to straight line trajectories of M² v. radial quantum number, all having a uniform slope of 1.1 ± 0.03 GeV² per excitation. Tensor and spin-orbit splitting is small. Resonances with L = J + 1 lie ∼ 100 MeV higher in mass than those with L = J - 1. Several states remain which do not fit naturally into this scheme, notably f₀(1500), f₀(2105), a broad 2⁺ state at 1980 ± 50 MeV and a broad 0^- resonance at 2190 ± 40 MeV. Their mass ratios agree within small errors (3-14%) with Lattice QCD calculations of Morningstar and Peardon for glueballs. The f₀(2105) appears strongly in the ηη channel, but not in ππ. This indicates exotic character. If interpreted in terms of a mixed state cos PHI(uubar + ddbar)/√2 + sin PHIssbar, then PHI = (65 ± 6) deg.

[en] 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

[en] Data from LEAR on p-barp → final states with I = 0, C = +1 reveal s-channel resonances corresponding to all qq-bar states (J = 0 to 5) expected in the mass range 1920-2400 MeV/c². They lie on parallel straight-line trajectories of s = M² v. radial excitation number. In addition there are four extra states which fail to fit on to these trajectories: f₀(1500), f₀(2105), f₂(1980) and η(2190). All have exotic properties and appear in J/Ψ radiative decays: this suggests glueball character. Their mass ratios agree within errors (typically ±4%) with recent Lattice Gauge calculations of Morningstar and Peardon for the lowest four glueballs

[en] There is a conflict between Argonne measurements of Δsigmasub(L) (pp) from 400 to 600 MeV and the real part of the corresponding forward amplitude between 150 and 600 MeV, and also with conventional wisdom about the dynamics of the inelastic channels. Proposed structure in Δσsub(L) (I = 0) is difficult to reconcile with existing np data. (author)

[en] Short communication

[en] Crystal Barrel data on pbarp → π⁰π⁰ are presented. Shapes of angular distributions are similar to data of Dulude et al, but show some systematic disagreements. Absolute normalisations disagree seriously. An amplitude analysis finds two alternative solutions. Both contain a J^PC 2⁺⁺ resonance with M = 2020 ± 40 MeV and Γ = 235 ± 70 MeV, tentatively identified as the qbarq ³F₂ state. Both solutions also require f₄(2050) and f₄(2300)

[en] Measurements of the spin-correlation parameter Asub(LL) at backward angles with errors of +- 0.02 would eliminate the present strong correlation between epsilonsub(1) and the ¹P₁ phase-shift, and stabilise the phase-shift solutions at 25 and 50 MeV. (author)

[en] Recent elastic scattering data from the meson factories are reviewed. The I = 1 phase shifts are now well determined up to 600 MeV, and I = 0 phase shifts to 500 MeV. The latest version of the Paris potential shows improved agreement with phase shifts, but there is room for further improvement. The ³D₃ and ³G₅ waves show a surprising difference in sign. The analysis of Grein and Kroll shows that the short-range interaction is considerably more complicated than previously believed, and 3sup(π) exchange plays a large and essential role. Experimental attention should now move to pion production amplitudes, for their relevance to N*s in nuclei and the possible existence of a pion condensate in nuclear matter at high densities. (orig.)

[en] New np elastic data of Abegg et al. stabilise I=0 phase shifts from 200 to 500 MeV. New data of Hutcheon et al. on K_SS for pp → dπ⁺ at 515 MeV agree well with the amplitude analysis of Bugg, Hasan and Shypit and correct a sign error in some published data of Cantale et al. A new analysis is reported of all current data of NN → NNπ from 420 to 800 MeV. A strong threshold cusp is observed in the NΔ S wave; it is not yet clear whether or not a bound state pole (quasi-deuteron) is required. In other partial waves, phases of amplitudes are negative or weakly positive and rule out dibaryon resonances. (orig.)