Soft or hard wave function in the end-point region?

The tail of the nucleon wave function at x $\to$ 1 is investigated. The dominance of this region by soft and hard effects is separately considered. Both contributions produce definite SU(6) symmetry breaking patterns which are compared with deep inelastic and large angle elastic scattering data. The analysis suggests the dominance of soft effects at present energies and momentum transfers

Spin system for the b-universality and the additive quark model

The possibility that the spin systems of b-universality and of the additive quark model coincide, as suggested by previous analyses [1, 2], is investigated. A comparison of the predictions with the data for the processes $0^{-}\frac{1}{2}^{+} \to 1^{-}\frac{3}{2}^{+}$ shows very good agreement with this hypothesis in both helicity and Gottfried-Jackson frames

The universal impact parameter hypothesis and the quark model

The introduction of b-universality into the additive quark model reduces the number of nonvanishing helicity amplitudes and offers an exact form of t-dependence for all amplitudes. Strong constraints on the additivity frame are obtained. Comparison with the data is made for the reaction $\pi^{+}p \to \pi ^{0}\Delta^{++}$. The obtained results rule out the Gottfried–Jackson frame as the additivity frame

Spin effects in hadronic collisions at large momentum transfers

The role of spin in hadron-hadron collisions at large p$_{1}$ is investigated. The short distance diagrams and the end-point (x $\to$ 1) contribution give phenomenologically similar results for the elastic nucleon-nucleon differential cross-section but differ significantly when looking at the spin-spin asymmetries. The spin analysis suggests the dominance of the end-point diagrams at large angles and present energies. The limits on the nucleon wave function are obtained from the comparison of spin effects in exclusive and inclusive reactions. Higher order results in exclusive channels are reviewed. In the inclusive production we propose a simple model of baryon polarization at large transverse momentum which accounts qualitatively for all experimental data in these processes. Other models are also reviewed. The whole investigation suggests that the spin effects are a relatively clear probe of the complicated hadron dynamics

Constraints on the spin system for two-body reactions

The quark additivity and a class of geometrical hypotheses concerning the spin dependence in two-body processes, are found to be compatible and consistent with experiment only when taken in the same spin frame