Structures in proton-proton scattering at intermediate energies

Summary  We discuss different structures observed in the proton-proton spin correlation parameters at θ=90° c.m. and in the spin-dependent cross-section differences $$\Delta \sigma _L $$ and $$\Delta \sigma _T $$ at intermediate energies. Elastic and inelastic contributions to the total cross-sections indicate $$\Delta \sigma _L $$ to be mainly elastic and $$\Delta \sigma _T $$ inelastic. Basing on the Saclay-Geneva phase shift analysis we have studied the energy dependence of the singlet-triplet scattering amplitudes at 0° and at 90° c.m. up to 1 GeV and calculated the singlet and triplet cross-sections up to 2200 MeV from experimental data. Only the spin-singlet partial amplitude shows a possible resonantlike structure at ≃560 MeV (total mass of 2.14 GeV); the spin-singlet total cross-section indicates another possible structure at ≃1.3 GeV (total mass of 2.44 GeV). Phase shift analysis results show an anticlock-wise structure in the Argand diagram for the spin singlet partial wave1 D 2 but no such behaviour in the3 F 3 partial wave.