abstract

For diffractive excitation of \(I=1/2\) nucleon resonances N\(^*\) by pions, N \(+\pi \to \) N\(^*+\pi \), the Gribov–Morrison rule is shown to follow from kinematics alone if \(t\)-channel helicity conservation is exact. Under this condition the production of unnatural-parity N\(^*\) is strongly suppressed by a mass factor. A similar result for diffractive N + N \(\to \) N\(^*\) + N follows from factorization. However, no corresponding effect can be found for diffractive excitation of mesons. The experimental situation is discussed in the light of this effect, which we conclude must play an important role in any realistic model for diffractive N \(\to \) N\(^*\) transitions, at least beyond the low N\(^*\) mass region.

abstract

It is possible to fit the single particle inclusive spectrum by a suitable temperature distribution. We discuss the resulting two-particle spectrum in this model and show that it contains the observed correlations.

abstract

A generalization of the Weizsäcker Williams method for massive fields with arbitrary tensor structure is considered. The resulting distribution of “equivalent quanta” has a particularly simple form, which is related to the field’s energy momentum tensor in the rest frame.

abstract

Within a multi-component cluster model including diffraction the presently observed KNO scaling is predicted to be real or transitory according to the energy-dependence of \(\sigma _{\rm el}/\sigma _{\rm t}\). When no diffraction is included at most an extremely slow approach to scaling is predicted.

abstract

Using the hard collision model and a simple parametrisation for jet fragmentation we derive expressions for same side and opposite side two-particle correlations and multiplicities associated with large transverse momentum trigger particles. Recent data on rapidity correlations and associated multiplicities can be well understood in such a model. We interpret this result as further evidence for the presence of jets in large transverse momentum reactions.

abstract

Using the universal impact parameter hypothesis and the additive quark model we derive several constraints on the amplitudes and density matrix elements of the process \(0^-\frac {1}{2}^+\to J^P\frac {3}{2}^+\). The comparison of these results with the data implies that the two models should be formulated in the same spin reference system. It is shown that the common frame need not be the \(s\)-channel helicity frame.

abstract

In is shown that the requirement of exact conservation of the isospin is in contradiction with the basic ingredients of the uncorrelated jet model. The nature of the strong correlations resulting from an attempt to build an isospin conserving uncorrelated jet model is studied. Modifications that make the correlations less visible are discussed.

abstract

Measurements of neutron spectra and of angular distributions of several neutron groups in the reaction \(^9\)Be(t,n)\(^{11}\)B are reported. Energies of tritium ions were 1.10, 1.30, and 1.70 MeV. Neutrons were registered by means of nuclear emulsion. It was found that in the investigated energy region the mechanism of compound nucleus plays a significant role.

abstract

On the basis of the analysis of gamma spectrum of \(A=159\) isobars the \(^{159}\)Yb isotope has been identified. Its half-life \(T_{1/2}=(1.75 \pm 0.20\)) min. has been measured. The \(^{159}\)Yb decay is followed by the emission of 166.1 and 177.0 keV gamma-rays.