Un modèle phénoménologique de la diffusion élastique méson π+ proton

Unified scheme for describing time delay and time advance in the interpolation of rotational bands of resonances

“…Remark: Let us note that the phase-shifts of formula (20) do not satisfy the asymptotic behaviour, for large values of ℓ, prescribed by formula (14). This derives from the fact that the amplitude given by formula (16), and, accordingly, the phase-shifts given by formula (20), are approximations which are faithful only for small values of ℓ. These approximations, however, are acceptable at low energy where a few terms of the partial-wave expansion are sufficient to describe the scattering amplitude.…”

“…iii) Representation (20) can describe, in principle, a sequence of resonances in various partialwaves.…”

“…ii) For the sake of preciseness, one should distinguish the quasi-nuclear phase-shifts δ ℓ from the purely nuclear phase-shifts δ * ℓ , which are those associated with the scattering between the same particles, with the same strong properties but without the Coulomb interaction [20]. It is rather intuitive, and can be rigorously proved, [20,21] that they differ by quantities proportional to the Sommerfeld parameter η = Z 1 Z 2 e 2 v . Even though η can be significantly large at low energies, nevertheless this fact does not prevent the phase-shifts δ ℓ from being treated as corresponding to a short range potential and retaining the main properties of interest for our analysis.…”

“…ii) For the sake of preciseness, one should distinguish the quasi-nuclear phase-shifts δ ℓ from the purely nuclear phase-shifts δ * ℓ , which are those associated with the scattering between the same particles, with the same strong properties but without the Coulomb interaction [20]. It is rather intuitive, and can be rigorously proved, [20,21] that they differ by quantities proportional to the…”