[en] Exclusive electroproduction of ρ⁰ mesons has been measured using the ZEUS detector at HERA in two Q² ranges, 0.25< Q²<0.85 GeV² and 3< Q²<30 GeV². The low-Q² data span the range 20< W<90 GeV; the high-Q² data cover the 40< W<120 GeV interval. Both samples extend up to four-momentum transfers of vertical stroke t vertical stroke =0.6 GeV². The distribution in the azimuthal angle between the positron scattering plane and the ρ⁰ production plane shows a small but significant violation of s-channel helicity conservation, corresponding to the production of longitudinally polarised (i.e. helicity zero) ρ⁰ mesons from transverse photons. Measurements of the 15 combinations of spin-density matrix elements which completely define the angular distributions are presented and discussed. (orig.)

[en] Historically, light quark meson spectroscopy with π and K beams has played an important role in establishing the current theory of quarks and gluons. It will continue to play an important role, along with meson production in complementary reactions, in the search for the full spectrum of QCD mesons such as glueballs, exotics, hybrids, and multi-quark states, in addition to the conventional q bar q mesons. Current experiments and the possibilities for future facilities are discussed

[en] The minimal rule for hadron scattering, proposed by Chou and Yang as a basic part of their fragmentation model, is tested for high-energy pp and π^-p data. We also calculate charge transfer for π^-p. In addition, we investigate the behavior of the fragmentation contribution to inclusive distributions in the central region, the rate of increase allowed by the minimal rule for extra energy-dependent contributions there, and factorization within the fragmentation concept

[en] Research from April 1981 to March 1982 is summarized in the areas of: πP interactions at 8 GeV; Fermilab experiment 299, π⁺, K⁺, P-proton experiments; charm search and vector meson production in 20 GeV γ-P interactions; and production of π^+-0, K^+-0, P, anti P, Lambda neutrals in multiparticle final states by tagged positive beams of 200 GeV particles on protons

[en] The elastic electroproduction of ρ mesons is studied at HERA with the H1 detector for a photon virtuality in the range 1< Q²<60 GeV² and for a hadronic centre of mass energy in the range 30< W<140 GeV. The shape of the (ππ) mass distribution in the ρ resonance region is measured as a function of Q². The full set of ρ spin density matrix elements is determined, and evidence is found for a helicity flip amplitude at the level of 8± 3% of the non-flip amplitudes. Measurements are presented of the dependence of the cross section on Q², W and t (the four-momentum transfer squared to the proton). They suggest that, especially at large Q², the γ^*p cross section develops a stronger W dependence than that expected from the behaviour of elastic and total hadron-hadron cross sections. (orig.)

[en] Results from the Fermilab 15-ft bubble chamber on the charged-particle multiplicity distributions produced in high-energy charged-current neutrino-proton interactions are presented. Comparisons are made to γp, ep, μp, and inclusive pp scattering. The mean hadronic multiplicity < n/subc/> appears to depend only on the mass of the excited hadronic state, independent of the mode of excitation. A fit to the neutrino data gives < n/subc/>= (1.09+-0.38) +(1.09+-0.03)lnW²

[en] The present status is described of πN phase shift analysis. The differences are shown between the phase shift analyses of the 1st generation and 2nd generation. The properties are studied of zero trajectories of πN amplitudes. (Z.J.)

[en] This book contains the contributions presented during the photon-photon collisions seminar

[en] The elastic γ-nucleon scattering represents an indirect powerful method for the nucleon structure investigation. Some theoretical aspects of this problem are treated in the presented thesis. After a general introduction into the subject and a short review of the up-to-date literature, the first chapter contains kinematics and dynamical preliminaries of reaction γ+N→γ+N. In chapter II, the low energy theorems are discussed and extended up to six power in the photon laboratory energies, ω; the six structure dependent constants which appear in the differential cross section in this order are defined and computed, and an extraction for the proton electromagnetic polarizabilities α,β from the experimental data is performed. A new dispersive analysis of the γ+N→γ+N process at photon laboratory energies lower than 450 Mev is introduced and used for numerical calculation in chapter III; some improvements are obtained in the comparison with the experimental data, with respect to other previous calculations. In the last chapter, two different sum rules for the difference (α-β) are established and numerically computed - these theoretical predictions agree with the values extracted from experience; based on the analyticity properties of the invariant amplitudes, an inequality is written down connecting an integral over the differential cross section of the process and the static properties of the nucleon (mass, charge, anomalous magnetic moment). (author)

[en] The method of obtaining the characteristics of charged particle groups: group multiplicity within the rapidly range, particle multiplicity in group distribution on width - was developed in the frame of the clan model